[OTEL-2552] Part 1 Datadog Extension (#39590)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Add initial PR for Datadog Extension
<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes #39589 

<!--Describe what testing was performed and which tests were added.-->
#### Testing
only limited tests for config; no extension functionality added yet
<!--Describe the documentation added.-->
#### Documentation
README.md, chloggen
<!--Please delete paragraphs that you did not use before submitting.-->

Author: jackgopack4

.chloggen/datadog-extension-proposal.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: new_component
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: datadogextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Introduce framework for Datadog Extension
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [39589]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

.github/CODEOWNERS

@@ -91,6 +91,7 @@ extension/azureauthextension/                                    @open-telemetry
 extension/basicauthextension/                                    @open-telemetry/collector-contrib-approvers @frzifus
 extension/bearertokenauthextension/                              @open-telemetry/collector-contrib-approvers @frzifus
 extension/cgroupruntimeextension/                                @open-telemetry/collector-contrib-approvers @mx-psi @rogercoll
+extension/datadogextension/                                      @open-telemetry/collector-contrib-approvers @jackgopack4 @dineshg13 @mx-psi @songy23
 extension/encoding/                                              @open-telemetry/collector-contrib-approvers @atoulme @dao-jun @dmitryax @MovieStoreGuy @VihasMakwana
 extension/encoding/avrologencodingextension/                     @open-telemetry/collector-contrib-approvers @thmshmm
 extension/encoding/awscloudwatchmetricstreamsencodingextension/  @open-telemetry/collector-contrib-approvers @axw @constanca-m

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -94,6 +94,7 @@ body:
       - extension/basicauth
       - extension/bearertokenauth
       - extension/cgroupruntime
+      - extension/datadog
       - extension/encoding
       - extension/encoding/avrologencoding
       - extension/encoding/awscloudwatchmetricstreamsencoding

.github/ISSUE_TEMPLATE/feature_request.yaml

@@ -88,6 +88,7 @@ body:
       - extension/basicauth
       - extension/bearertokenauth
       - extension/cgroupruntime
+      - extension/datadog
       - extension/encoding
       - extension/encoding/avrologencoding
       - extension/encoding/awscloudwatchmetricstreamsencoding

.github/ISSUE_TEMPLATE/other.yaml

@@ -88,6 +88,7 @@ body:
       - extension/basicauth
       - extension/bearertokenauth
       - extension/cgroupruntime
+      - extension/datadog
       - extension/encoding
       - extension/encoding/avrologencoding
       - extension/encoding/awscloudwatchmetricstreamsencoding

.github/ISSUE_TEMPLATE/unmaintained.yaml

@@ -93,6 +93,7 @@ body:
       - extension/basicauth
       - extension/bearertokenauth
       - extension/cgroupruntime
+      - extension/datadog
       - extension/encoding
       - extension/encoding/avrologencoding
       - extension/encoding/awscloudwatchmetricstreamsencoding

.github/component_labels.txt

@@ -72,6 +72,7 @@ extension/azureauthextension extension/azureauth
 extension/basicauthextension extension/basicauth
 extension/bearertokenauthextension extension/bearertokenauth
 extension/cgroupruntimeextension extension/cgroupruntime
+extension/datadogextension extension/datadog
 extension/encoding extension/encoding
 extension/encoding/avrologencodingextension extension/encoding/avrologencoding
 extension/encoding/awscloudwatchmetricstreamsencodingextension extension/encoding/awscloudwatchmetricstreams

extension/datadogextension/Makefile

@@ -0,0 +1 @@
+include ../../Makefile.Common

extension/datadogextension/README.md

@@ -0,0 +1,18 @@
+# Datadog Extension
+<!-- status autogenerated section -->
+| Status        |           |
+| ------------- |-----------|
+| Stability     | [development]  |
+| Distributions | [] |
+| Issues        | [![Open issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aopen%20label%3Aextension%2Fdatadog%20&label=open&color=orange&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aextension%2Fdatadog) [![Closed issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aclosed%20label%3Aextension%2Fdatadog%20&label=closed&color=blue&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Aextension%2Fdatadog) |
+| [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@jackgopack4](https://www.github.com/jackgopack4), [@dineshg13](https://www.github.com/dineshg13), [@mx-psi](https://www.github.com/mx-psi), [@songy23](https://www.github.com/songy23) |
+
+[development]: https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/component-stability.md#development
+<!-- end autogenerated section -->
+
+This is the initial version of the Datadog Extension. It is in development and not guaranteed to work in any specific way prior to collector infrastructure monitoring features being announced or launched by Datadog.
+
+You can configure this extension in service, using the following configuration values:
+`api::key`: a Datadog API Key, required
+`api::site`: your Datadog site value (e.g. us5.datadoghq.com), defaults to "datadoghq.com"
+`hostname`: custom hostname; if you do not specify one, the extension will try to infer one. Note: this must match any hostname value set in the `host_metadata` section of Datadog Exporter, if also enabled in your collector.

extension/datadogextension/config.go

@@ -0,0 +1,43 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package datadogextension // import "github.com/open-telemetry/opentelemetry-collector-contrib/extension/datadogextension"
+
+import (
+	"fmt"
+	"strings"
+
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/confighttp"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/datadogextension/internal/httpserver"
+	datadogconfig "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/datadog/config"
+)
+
+var _ component.Config = (*Config)(nil)
+
+// Config contains the information necessary for enabling the Datadog Extension.
+type Config struct {
+	confighttp.ClientConfig `mapstructure:",squash"`
+	// Define the site and API key (and whether to fail on invalid API key) in API.
+	API datadogconfig.APIConfig `mapstructure:"api"`
+	// If Hostname is empty extension will use available system APIs and cloud provider endpoints.
+	Hostname string `mapstructure:"hostname"`
+	// HTTPConfig is v2 config for the http metadata service.
+	HTTPConfig *httpserver.Config `mapstructure:"http"`
+}
+
+// Validate ensures that the configuration is valid.
+func (c *Config) Validate() error {
+	if c.API.Site == "" {
+		return datadogconfig.ErrEmptyEndpoint
+	}
+	if c.API.Key == "" {
+		return datadogconfig.ErrUnsetAPIKey
+	}
+	invalidAPIKeyChars := datadogconfig.NonHexRegex.FindAllString(string(c.API.Key), -1)
+	if len(invalidAPIKeyChars) > 0 {
+		return fmt.Errorf("%w: invalid characters: %s", datadogconfig.ErrAPIKeyFormat, strings.Join(invalidAPIKeyChars, ", "))
+	}
+	return nil
+}