Slow DomainClassesRelationsEditorProvider

It asks if class is a GORM bean, which requires resolve of class annotations, which is slow, and it's happening on EDT.

**Workaround**: enable `grails.advanced.mode` in the Registry.

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*Imported from [IDEA-184140](https://youtrack.jetbrains.com/issue/IDEA-184140) · Type: Performance Problem · Votes: 1*
*Comments, attachments, dates and reporter are not part of the export — follow the link above for the full history.*

Start by locating DomainClassesRelationsEditorProvider and tracing the check that determines whether a class is a GORM bean. Reproduce the slowdown with grails.advanced.mode disabled, then inspect how annotation resolution is triggered on the EDT. Done means the editor no longer performs this slow work synchronously there, with a regression test if the existing test structure supports it.

Written by the indexing model from the issue text.