Warn on No Constraints

[SentryMan]

• Will log a compiler warning if processed class has no constraints

part of #333

[rbygrave]

#333 is not clear yet as to the motivations yet. It isn't clear to me why we are doing this and what the implications are.

[SentryMan]

warning when you have no constraints is common sense

[rbygrave]

will only cascade if valid annotation is present

This to me is a fairly significant behaviour change / bug fix. As such it really needs to be in it's own PR with it's own title rather than part of "Warn on No Constraints".

I think we need to split that out into a separate PR.

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Edit: Note that it wasn't actually a behaviour change, but instead just generated extra code that was never used. I interpreted that part incorrectly.

[SentryMan]

This to me is a fairly significant behaviour change / bug fix.

I fail to understand, if a field/TYPE_USE field is not annotated with @Valid there is no circumstance where it should have an adapter generated. The adapter would just be unused because there is no code path where it is called

I think we need to split that out into a separate PR.

#340