adds server url template abnf

[baywet]

partial #3256
related #4244

[baywet]

CC @char0n @ralfhandl @handrews

[handrews]

After discussion in TDC we agreed that pchar is not the right rule and we should use the general literals per RFC6570.

[baywet]

@handrews @char0n @ralfhandl I think we're ready for final review here :)

[ralfhandl]

Align with https://www.rfc-editor.org/errata/eid6937

[char0n]

LGTM, I've tested it as well, compiles and parses correctly.

[handrews]

Random question- why does this PR start with "docs:"? It's a spec PR, not a docs PR. I keep overlooking it because of this.

[baywet]

Random question- why does this PR start with "docs:"? It's a spec PR, not a docs PR. I keep overlooking it because of this.

Muscle memory: on most repos I work on, we follow semantic commits. And usually when I touch Md files there, it's documentation.

GitHub CLI: -f uses the first commit when creating a PR.

[handrews]

@baywet thank you for satisfying my curiosity! Yeah, this project is a little unusual in that the spec markdown is really the "source". "Docs" to me are things like CONTRIBUTING.md and the README.