Differentiate between empty structures and components that can take on any value

[mgyucht]

Changes

Currently, the SDK doesn't distinguish between empty structures and components that can take any value. As a result, the SDK uses type any for fields that should really have a type of struct{} or *struct{} (or an equivalent type). This PR updates the OpenAPI generator code to distinguish between these two cases.

Additionally, we update the generation of SDK structures to include empty types. This includes some types that are not currently used in the SDK, mainly empty responses because the generated API calls for methods with an empty response just omits the response return value entirely.

Two changes we should consider for later:

1. Include empty response types in the return value for API calls. Even though they are empty, it means that adding anything to an empty response is a breaking change for SDK users.
2. Combine emptyTypes and types. Users can always filter out empty types based on Entity.IsEmpty. This reduces unnecessary complexity in the generator. However, first, the other SDKs need to be updated to handle this case.

This also includes some changes from the Settings team and Files team, but it is necessary to update as there were issues with structures that were incorrectly annotated with x-databricks-any.

Tests

• make test passing
• make fmt applied
• relevant integration tests applied

[codecov-commenter]

Codecov Report

Attention: 202 lines in your changes are missing coverage. Please review.

Comparison is base (30881c6) 18.62% compared to head (4e6742a) 18.45%.

Files	Patch %	Lines
service/settings/model.go	0.00%	101 Missing ⚠️
service/settings/impl.go	0.00%	75 Missing ⚠️
service/settings/api.go	0.00%	20 Missing ⚠️
openapi/code/package.go	40.00%	2 Missing and 1 partial ⚠️
openapi/model.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #821      +/-   ##
==========================================
- Coverage   18.62%   18.45%   -0.17%     
==========================================
  Files         117      117              
  Lines       21824    22023     +199     
==========================================
+ Hits         4064     4065       +1     
- Misses      17510    17708     +198     
  Partials      250      250              

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[mgyucht]

This is a bugfix, as the empty type identity is based on the type name, not the reference to the Named struct.

[hectorcast-db]

Looks good