Improve JSON validation schema generation in Microsoft.AspNetCore.OpenApi

[captainsafia]

#41238 introduced a very reductive schema generation interface for the OpenApi package.

Moving forward we want to make this API a lot more robust which includes generating the full schema (types, formats, and constraints) for Types that are provided in MethodInfo including:

• Accounting for nullability
• Accounting for default values
• Accounting for types and formats to match JSON validation
• Accounting for types with TryParse methods

[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 7 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
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[captainsafia]

With #42169 and domaindrivendev/Swashbuckle.AspNetCore#2441, we're in decent shape here for .NET 7. There are still a few small issues I need to fix on the Microsoft.AspNetCore.OpenApi side, but we're generating sufficient schemas here.

Long-term, we want to explore more foundational support for generating JSON schemas (which OpenAPI schemas are a derivative of) in either System.Text.Json (ref) or Microsoft.OpenAPI (ref).