Expose max_header_value_length for http listeners

[DomasM]

Proposed Changes

Fix for #2267 - expose max_header_value_length, so that websocket connection can be established from frontend applications with bigger cookies.

Types of Changes

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• Bugfix (non-breaking change which fixes issue [Bug]: Websockets upgrade request: HTTP 431: Request Header Fields Too Large with big cookies #2267)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (correction or otherwise)
• Cosmetics (whitespace, styles...)
• DevOps (Build scripts, pipelines...)

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Further Comments

I have never done any work in Erlang, did not set up local dev env, changes are done by mirroring #2161
I will create another PR in docs repo to save other devs some time next time.

[mths1]

I'd recommend that you ignore all the http and https for now, and focus on ws and wss. You'd need to add your new setting to that part of the schema, as well as in vmq_schema.erl. Once you got that working, you can consider to introduce the setting also for http and https (and yes, it means code duplication)

[DomasM]

As simple as it seems, but I was unable to pass settings from vernemq.conf to vmq_ranch_config.erl line 366 as values don't appear in Opts there. Looking at the other settings, I can't figure out what's the difference. I won't be able to allocate more time to this issue in the foreseeable weeks, so my suggestion is to increase default values and set them explicitly in verne code instead of depending on ranch defaults:

max_header_value_length  4096 -> 16384
max_request_line_length  8000 -> 16384

[ioolkos]

@DomasM I'll look into it. Thank you for your effort so far!

[ioolkos]

Closing in favour of #2289. Thanks again for kicking this off, @DomasM.