[FIX] FromRequest() JSON content type validation

[quetzyg]

Problem

The logic to check if a request contains JSON is too restrictive. Since only the exact application/json string is considered valid, when the Content-Type header contains values such as application/vnd.api+json or application/json; charset=UTF-8, the request body is dismissed.

Another problem is that there are other JSON MIME types besides application/json.

If we do a quick search here, we can find 200+ MIME types related to JSON.

Solution

The mime type check logic has been improved by using a regular expression. Here's a brief explanation:

(?i)  --> case insensitive matches
application/ --> the only type we care about and the type/subtype separator
((\w|\.|-)+\+)? --> this group may exist with one or more (a-z, 0-9, _, . and -) characters and always with a + at the end
json --> the final part of the subtype
(-seq)? --> some JSON MIME types have this suffix

Caveats

The current regular expression isn't strict about the combination of allowed characters in a subtype, which means that non-existent/unofficial MIME types, like application/foobar+json or application/vnd.123+json are considered valid.

For the sake of simplicity, I think that's a good trade-off. It also means that when new JSON MIME types are added in the future, this logic should require low maintenance, if any.

Task items:

• Improve JSON Content-Type check logic in FromRequest();
• Update existing tests;

[coveralls]

Pull Request Test Coverage Report for Build 325982699

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.874%

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Totals
Change from base Build 297365813:	0.0%
Covered Lines:	2498
Relevant Lines:	2661

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💛 - Coveralls

[quetzyg]

Cheers @inhere 👍