More thorough support for retrieving OpenAPI routes in a case-sensitive manner

[sander1095]

More thorough support for retrieving OpenAPI routes in a case-sensitive manner

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This PR fixes some oversights from #59199 around retrieving OpenAPI documents case-insensitively.

Description

This PR modifies missed files from #59199 that use the registered document name as a key for retrieving services or options. This needs to be done case-insensitively to:

• Ensure documents can be retrieved correctly
  • Trying to retrieve services around OpenAPI documents that are registered with a differently cased document name, will result in an exception, which is not desired!
• Ensure documents are generated and retrieved with the correct OpenAPI version
  • If the configuration options are retrieved with an incorrectly cased document name argument, a default instance of OpenApiOptions is returned, which might contain different settings than what the user had configured.

This PR also adds some more comments and improves existing ones based on the previous PR around case-insensitive OpenAPI document names.

Fixes #59175

[captainsafia]

Thanks for catching this and following up with a PR!

This has got me thinking that we should audit other places where we pass in documentName in the same way. As a result, it looks like we'll also want to make a change in OpenApiDocumentProvider. The same test around the API version should work here.

[sander1095]

@captainsafia I've implemented your requested changes, added extra comments, improved existing ones and updated the title and description of PR to better reflect the changes.

Let me know if you want me to do anything else! :)