feat(mailgun): Add EU region support and UI configuration options #7866

Job	Run time
build-frontend	17s
prepare-test-environment	3m 16s
build-backend	16s
run-postgresql-without-redis / run-tests	4m 36s
run-mysql-with-redis / run-tests	4m 36s
run-sqlite-without-redis / run-tests	4m 37s
	17m 38s

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