Fixes #2900 - Checks slur regex to see if it is too permissive (#3146)

Fixes #2900 - Checks slur regex to see if it is too permissive (#3146)

* Fixes #2900 - Checks slur regex to see if it is too permissive along with small validation organization

* Clean up variable names, add handler for valid empty string usecase

* Update tests

* Create validation function and add tests

* Test clean up

* Use payload value vs local site value to prevent stunlocking

* Remove println added while testing

* Fall back to local site regex if not provided from request

* Attempt clean up of flaky comment_view tests

* Pull in latest submodule

* Move application, post check into functions, add more tests and improve test readability

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Co-authored-by: Nutomic <me@nutomic.com>