refactor: rename variables, add a comment

Author: honzajavorek

lib/mixins/validatable-http-message.js

@@ -1,6 +1,6 @@
 const jph = require('json-parse-helpfulerror');
 const mediaTyper = require('media-typer');
-const contentTypeModule = require('content-type');
+const contentType = require('content-type');
 const isset = require('../utils/isset');
 const validators = require('../validators');
 
@@ -425,18 +425,21 @@ but body is not a parseable JSON:\n${error.message}\
     );
   }
 
-  isJsonContentType(contentType) {
-    if (!contentType) {
+  isJsonContentType(contentTypeValue) {
+    if (!contentTypeValue) {
       return false;
     }
     try {
-      const { type } = contentTypeModule.parse(`${contentType}`);
+      const { type } = contentType.parse(`${contentTypeValue}`);
       const parsed = mediaTyper.parse(type);
       return (
         (parsed.type === 'application' && parsed.subtype === 'json')
         || parsed.suffix === 'json'
       );
     } catch (e) {
+      // The Content-Type value is basically a user input, it can be any
+      // kind of rubbish, and it is neither this function's nor Gavel's problem
+      // if it's invalid
       return false;
     }
   }