Bug fixes and validation improvements for fe_integration resource

[mrmauer]

Resolves issues mentioned here.

After PR

1. We validate urls and url paths for the fe_integration resource
2. We correctly parse responses when fetching fe_integration info for staging environments
3. We check whether application url is localhost with http and set the application_url.type appropriately if so. We also perform the reverse when updating the state on Reads.
4. We add unit tests to all utils, including those used for point 1 above.

[andrew-propelauth]

lgtm!