Wrong http status assigned to status.FailedPrecondition

[pboguslawski]

Describe the bug
status.InvalidArgument and status.FailedPrecondition are different statuses but are mapped to the same http.StatusBadRequest:

https://github.com/swaggest/rest/blob/master/error.go#L130
https://github.com/swaggest/usecase/blob/master/status/status.go#L97

Expected behavior
status.FailedPrecondition should be mapped to http.StatusPreconditionFailed.

Additional context
Related: #145

[vearutop]

Interesting, original source of mapping is https://github.com/googleapis/googleapis/blob/f36c65081b19e0758ef5696feca27c7dcee5475e/google/rpc/code.proto#L127, I wonder was it a mistake in google repo or deliberate decision.

[pboguslawski]

Seems that FAILED_PRECONDITION description in googleapis is not well mapped to HTTP status code (400 means client side problem) or they have some reason for merging different 4xx errors into one 400.

Consider replacing 400->412 in swaggest for status.FailedPrecondition to allow API clients to distinguish failed preconditions (i.e. client tried to update resource with lost update protection detection and update failed) from bad client requests (i.e. invalid argument that may indicate bug in client).

[pboguslawski]

After this mod, when 304 is added to possible error responses with...

u.SetExpectedErrors(status.Internal, rest.HTTPCodeAsError(http.StatusNotModified))

...openapi.json contains non-empty body for 304 but should not.