otlp receiver checks the whole value of content-type http header matches. It should check only the media-type part of the header

[shahrajesh2006]

Describe the bug
when the http header content-type value is "application/json;v=1" or "application/json; charset=utf-8"
receiver throws below error
"415 unsupported media type, supported: [application/json, application/x-protobuf"

Steps to reproduce
send http header content-type value "application/json;v=1"

What did you expect to see?
successful http 200 response

What did you see instead?
"415 unsupported media type, supported: [application/json, application/x-protobuf"

What version did you use?
Version: latest

What config did you use?
Config: (e.g. the yaml config file)

Environment
OS: Amazon Linux
Compiler(if manually compiled): (e.g., "go 14.2")

Additional context
Add any other context about the problem here.

[atoulme]

@macno is working on a fix. I'll try to assign to him.

[macno]

Yep, PR #7451 should be ready to be merged