Require meta-annotations with source rentetion for Immutables styles

[pkoenig10]

Update ImmutablesStyleCollision check to make it stricter by requiring meta-annotations with source retention.

Use inline annotations or meta-annotations with other retention policies forces a consumers to add an Immutables annotations compile dependency to avoid compile warnings.

For more details see immutables/immutables#291 - specifically the recommendation not to use inline styles.

Also the recommended way for the styles to be applied is via package (possibly even some parent package) or via a custom style annotation (which also may be attached to class or to a package). Inline styles should be used only for experimentation.

We manually made this change in our repos, some examples:

• Use SOURCE retention for immutables style annotations tracing-java#691
• Use SOURCE retention for immutables style annotations tritium#1006
• Use SOURCE retention for immutables style annotations dialogue#1145

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Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Update ImmutablesStyleCollision check to require meta-annotations with source retention.

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[pkoenig10]

Would still like a review of this.

[pkoenig10]

Changed to WARNING so users have an escape hatch

[fawind]

Looks good. Yeah, makes sense to use WARNING initially. Can always raise this in the future if necessary.