Add documentation around opening a port, and registering a haproxy service

[ewdurbin]

Can you add these to guides/index.rst so they're navigable?

[ewdurbin]

I'm getting errors building this locally:

$ tox -e docs
docs: commands[0]> sphinx-build -W -b html -d /Users/ee/src/psf-salt/.tox/docs/tmp/doctrees docs docs/_build/html
Running Sphinx v5.3.0
myst v0.18.1: MdParserConfig(commonmark_only=False, gfm_only=False, enable_extensions=[], disable_syntax=[], all_links_external=False, url_schemes=('http', 'https', 'mailto', 'ftp'), ref_domains=None, highlight_code_blocks=True, number_code_blocks=[], title_to_header=False, heading_anchors=None, heading_slug_func=None, footnote_transition=True, words_per_minute=200, sub_delimiters=('{', '}'), linkify_fuzzy_links=True, dmath_allow_labels=True, dmath_allow_space=True, dmath_allow_digits=True, dmath_double_inline=False, update_mathjax=True, mathjax_classes='tex2jax_process|mathjax_process|math|output_area')
building [mo]: targets for 0 po files that are out of date
building [html]: targets for 16 source files that are out of date
updating environment: [new config] 16 added, 0 changed, 0 removed
reading sources... [100%] ssl                                                                                             

Warning, treated as error:
/Users/ee/src/psf-salt/docs/guides/haproxy-registration-guide.md:1:Document headings start at H2, not H1 [myst.header]
docs: exit 2 (0.45 seconds) /Users/ee/src/psf-salt> sphinx-build -W -b html -d /Users/ee/src/psf-salt/.tox/docs/tmp/doctrees docs docs/_build/html pid=50986
  docs: FAIL code 2 (0.47=setup[0.02]+cmd[0.45] seconds)
  evaluation failed :( (0.57 seconds)

[ewdurbin]

Thanks @cegerhardson, this looks comprehensive!