tests: Add assertion for model.server_url in test_init

[pushkarscripts]

What does this PR do, and why?

Adds the missing assertion for model.server_url in test_init, resolving the existing FIXME comment.

Also extends coverage with a parametrized test covering different base_url scheme and netloc combinations to ensure correct normalization behavior.

External discussion & connections

• Discussed in #zulip-terminal in topic PR: Add test for model.server_url in test_init
• Fully fixes #
• Partially fixes issue #
• Builds upon previous unmerged work in PR #
• Is a follow-up to work in PR #
• Requires merge of PR #
• Merge will enable work on #

How did you test this?

• Manually - Behavioral changes
• Manually - Visual changes
• Adapting existing automated tests
• Adding automated tests for new behavior (or missing tests)
• Existing automated tests should already cover this (only a refactor of tested code)

Self-review checklist for each commit

• It is a minimal coherent idea
• It has a commit summary following the documented style (title & body)
• It has a commit summary describing the motivation and reasoning for the change
• It individually passes linting and tests
• It contains test additions for any new behavior
• It flows clearly from a previous branch commit, and/or prepares for the next commit

[clado]

lgtm! thanks for your work on improving it!! :)
maybe @neiljp you want to take a look, especially as the original writer of the fixme?

[clado]

wait, quick addendum (I am "commit undisciplined" lol) but it may be a good idea to turn your two commits into one commit, since they're pretty much the same idea? (And, since I'd argue that it's only the second commit that truly resolved the fixme that was removed in the first commit.)

The Zulip documentation discussing squashing commits in this manner, but perhaps not in enough detail to follow if you've never done an interactive rebase before... Totally unsure whether that describes you or not, but want to encourage you to ask for help if you need it! 🫡

[pushkarscripts]

wait, quick addendum (I am "commit undisciplined" lol) but it may be a good idea to turn your two commits into one commit, since they're pretty much the same idea? (And, since I'd argue that it's only the second commit that truly resolved the fixme that was removed in the first commit.)

The Zulip documentation discussing squashing commits in this manner, but perhaps not in enough detail to follow if you've never done an interactive rebase before... Totally unsure whether that describes you or not, but want to encourage you to ask for help if you need it! 🫡

Thanks for the suggestion.
That makes sense since the second commit completes the fix.

I’ll squash them into a single commit 👍