Update members namespace id constraints

What does this MR do and why?

Describe in detail what your merge request does and why.

#349640 (closed)

• add NOT NULL constraint for member_namespace_id column
• change add_concurrent_foreign_key :members, :namespaces, column: :namespace_id, on_delete: :nullify to add_concurrent_foreign_key :members, :namespaces, column: :namespace_id, on_delete: :cascade

up:

main: == 20220914005141 ChangeNamespaceIdNotNullInMembers: migrating ================
main: -- current_schema()
main:    -> 0.0016s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- current_schema()
main:    -> 0.0002s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- execute("ALTER TABLE members\nADD CONSTRAINT check_508774aac0\nCHECK ( member_namespace_id IS NOT NULL )\nNOT VALID;\n")
main:    -> 0.0014s
main: == 20220914005141 ChangeNamespaceIdNotNullInMembers: migrated (0.0255s) =======

main: == 20220914010233 ChangeMembersNamespaceForeignKeyOnDeleteConstraint: migrating 
main: -- transaction_open?()
main:    -> 0.0000s
main: -- foreign_keys(:members)
main:    -> 0.0024s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- execute("ALTER TABLE members\nADD CONSTRAINT fk_2f85abf8f1\nFOREIGN KEY (member_namespace_id)\nREFERENCES namespaces (id)\nON DELETE CASCADE\nNOT VALID;\n")
main:    -> 0.0040s
main: == 20220914010233 ChangeMembersNamespaceForeignKeyOnDeleteConstraint: migrated (0.0088s) 

down:

main: == 20220914010233 ChangeMembersNamespaceForeignKeyOnDeleteConstraint: reverting 
main: -- transaction_open?()
main:    -> 0.0000s
main: -- foreign_keys(:members)
main:    -> 0.0034s
main: -- remove_foreign_key(:members, {:column=>:member_namespace_id, :name=>"fk_2f85abf8f1"})
main:    -> 0.0023s
main: == 20220914010233 ChangeMembersNamespaceForeignKeyOnDeleteConstraint: reverted (0.0479s) 

main: == 20220914005141 ChangeNamespaceIdNotNullInMembers: reverting ================
main: -- transaction_open?()
main:    -> 0.0000s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- execute("ALTER TABLE members\nDROP CONSTRAINT IF EXISTS check_508774aac0\n")
main:    -> 0.0003s
main: == 20220914005141 ChangeNamespaceIdNotNullInMembers: reverted (0.0014s) =======

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