Schedule database indexes on `members`, `project_authorizations`

What does this MR do and why?

Schedules two database indexes for !117642 (merged).

Query plans

Indexes

members

CREATE INDEX index_members_on_source_and_type_and_access_level ON members USING btree (source_id, source_type, type, access_level);

postgres.ai (Duration: 4.342 min)

project_authorizations

CREATE UNIQUE INDEX index_project_authorizations_on_project_user_access_level ON project_authorizations USING btree (project_id, user_id, access_level);

postgres.ai (Duration: 39.845 min)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #395545 (closed)