fix: collect routes from Host(#2118)

[magiskboy]

Summary

When developer defines Host in application, routes of Host cannot be generated to OpenAPI schemas so this PR fixes that.

I collect routes (in get_endpoints) in Host class when generating OpenAPI schemas

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.

[Kludex]

Thanks @magiskboy :)