[receiver/awsfirehose] Fix decoding for OTLP-formatted metrics (#39720)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Fix decoding for OTLP-formatted metrics. The unmarshaler for
OTLP-formatted metrics uses the
[awscloudwatchmetricstreamsencodingextension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/encoding/awscloudwatchmetricstreamsencodingextension)
to unmarshal the metrics, instead of a custom unmarshaler.

<!-- Issue number (e.g. #1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes #39462.

<!--Describe what testing was performed and which tests were added.-->
#### Testing

Unit tests fixed.

<!--Describe the documentation added.-->
#### Documentation

README updated with a warning.

Author: constanca-m

.chloggen/awsfirehosereceiver-fix-otlp.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: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: awsfirehosereceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix decoding for OTLP-formatted metrics.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [39462]
+
+# (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: OTLP-formatted metrics were not being decoded correctly until now.
+
+# 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]

receiver/awsfirehosereceiver/README.md

@@ -88,5 +88,8 @@ For example:
 ```
 
 ### otlp_v1
+
 The OTLP v1 encoding as produced by CloudWatch metric streams.
 See [documentation](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch-metric-streams-formats-opentelemetry-100.html) for details.
+
+

receiver/awsfirehosereceiver/go.mod

@@ -3,9 +3,9 @@ module github.com/open-telemetry/opentelemetry-collector-contrib/receiver/awsfir
 go 1.23.0
 
 require (
-	github.com/gogo/protobuf v1.3.2
 	github.com/json-iterator/go v1.1.12
 	github.com/klauspost/compress v1.18.0
+	github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding/awscloudwatchmetricstreamsencodingextension v0.0.0-00010101000000-000000000000
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest v0.126.0
 	github.com/stretchr/testify v1.10.0
 	go.opentelemetry.io/collector/component v1.32.0
@@ -19,6 +19,7 @@ require (
 	go.opentelemetry.io/collector/consumer v1.32.0
 	go.opentelemetry.io/collector/consumer/consumererror v0.126.0
 	go.opentelemetry.io/collector/consumer/consumertest v0.126.0
+	go.opentelemetry.io/collector/extension v1.32.0
 	go.opentelemetry.io/collector/pdata v1.32.0
 	go.opentelemetry.io/collector/receiver v1.32.0
 	go.opentelemetry.io/collector/receiver/receivertest v0.126.0
@@ -29,14 +30,16 @@ require (
 
 require (
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
-	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/foxboron/go-tpm-keyfiles v0.0.0-20250323135004-b31fac66206e // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-viper/mapstructure/v2 v2.2.1 // indirect
 	github.com/gobwas/glob v0.2.3 // indirect
+	github.com/goccy/go-json v0.10.5 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang/snappy v1.0.0 // indirect
 	github.com/google/go-tpm v0.9.4 // indirect
 	github.com/google/uuid v1.6.0 // indirect
@@ -48,9 +51,10 @@ require (
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding v0.126.0 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.126.0 // indirect
 	github.com/pierrec/lz4/v4 v4.1.22 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/rs/cors v1.11.1 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/collector/client v1.32.0 // indirect
@@ -95,3 +99,7 @@ replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil
 replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest => ../../pkg/pdatatest
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/golden => ../../pkg/golden
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding => ../../extension/encoding
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/extension/encoding/awscloudwatchmetricstreamsencodingextension => ../../extension/encoding/awscloudwatchmetricstreamsencodingextension