Validate member namespace id constraints

What does this MR do and why?

Describe in detail what your merge request does and why.

#371095 (closed)

#377433 (comment 1139215782)

In !102843 (merged) we add a not null constraint and in !93240 (merged) we add a foreign key with validate: false. In this MR, validate those constraints.

• Migration file 1: Re-add the check constraint (not valid). ✅ !102843 (merged)
• Migration file 2: Fix the 453 (maybe we get some extra records here due to the missing CHECK constraint) records by backfilling the data or removing the member records (inline). ✅ !99080 (merged)
• Migration file 3: Validate the check constraint and the FK (fk_2f85abf8f1). <- this MR
• Migration file 4: Drop the FK with the SET NULL clause (fk_aa82dcc1c6). !97929 (closed)

% rails db:migrate
main: == 20220916072304 ValidateNotNullConstraintOnMembersNamespaceId: migrating ====
main: -- current_schema()
main:    -> 0.0031s
main: -- execute("SET statement_timeout TO 0")
main:    -> 0.0003s
main: -- execute("ALTER TABLE members VALIDATE CONSTRAINT check_508774aac0;")
main:    -> 0.0029s
main: -- execute("RESET statement_timeout")
main:    -> 0.0005s
main: == 20220916072304 ValidateNotNullConstraintOnMembersNamespaceId: migrated (0.0155s) 

main: == 20220916073539 ValidateFkMembersNamespaceId: migrating =====================
main: -- foreign_keys(:members)
main:    -> 0.0044s
main: -- execute("ALTER TABLE members VALIDATE CONSTRAINT fk_2f85abf8f1;")
main:    -> 0.0205s
main: == 20220916073539 ValidateFkMembersNamespaceId: migrated (0.0254s) ============


% rails db:rollback:main STEP=2 
main: == 20220916073539 ValidateFkMembersNamespaceId: reverting =====================
main: == 20220916073539 ValidateFkMembersNamespaceId: reverted (0.0006s) ============

main: == 20220916072304 ValidateNotNullConstraintOnMembersNamespaceId: reverting ====
main: == 20220916072304 ValidateNotNullConstraintOnMembersNamespaceId: reverted (0.0000s) 

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