[BUG][JAVA] --type-mappings for string+date are not working

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

When we specify --type-mappings string+date=LocalDate as CLI argument then it will generate invalid type for fields specified as:

type: string
format: date

It will generate private ModelLocalDate expiresOn; where ModelLocalDate does not exists

Update:
If I use --type-mappings string+date=Instant then it works. So it appears that maybe defining something what is default value will cause issues.

openapi-generator version

Tested this on:

• 7.0.0, 7.0.1 - it does NOT work here
• 6.6.0, 6.4.0 - it works here

OpenAPI declaration file content or url

Start with the Java generator CLI path and reproduce the provided OpenAPI schema using --type-mappings string+date=LocalDate on versions 7.0.0 or 7.0.1. Compare the generated model type with versions 6.6.0 or 6.4.0 and check the generator's existing type-mapping tests. Done means a string/date field generates LocalDate rather than the nonexistent ModelLocalDate type.