From commit 85cc1729

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

It will hold notification setting per group or per project. It will
allow get rid of notification level stored in Member model
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

According to endbosses' suggestions.

On PostgreSQL the index is created concurrently.

Fixes gitlab-org/gitlab-ce#14325

The user has the rights of a public user execpt it can never create a project,
 group, or team. Also it cant view internal projects.

This also includes e.g. the appearances table which apparently wasn't
already included in the schema.

This allows the LIKE condition to use an index. Without a GIN + trigram
index LIKE queries using a wildcard at the start _won't_ use an index
and instead perform a sequence scan.