Improve SQL query for "Custom abilities for group memberships"

The following discussions from !125652 (merged) should be addressed:

• @jessieay started a discussion: (+1 comment)

  Self-review comment: I removed this line because I could not find any instances of read_vulnerability being called on a group. And this line was only recently added in Jarka's refactor MR but I think that was accidental: !113377 (merged)

  admin_vulnerability is used for groups, see !66312 (diffs)

• @bwill started a discussion: (+1 comment)

  Thought (non-blocking): User is an omniscient class. Could this logic be encapsulated somewhere else?

• @minac started a discussion:

  suggestion (non-blocking): I think this method should be private as there is no reference to it from outside, right?

• @krasio started a discussion:

  namespaces.tracersal_ids also includes namespaces.id as it's last element, I think we can skip this node as the next one will fetch the matching rows anyway, right?

• @krasio started a discussion: (+2 comments)

  What is the goal of limit(1) here? Is it possible this way we exclude a row where one of the columns has TRUE value, and this way end up with the default FALSE?

• @krasio started a discussion: (+4 comments)

  I think we can rewrite this query like

  SELECT
      groups.id,
      Bool_or(custom_permissions.read_vulnerability) AS read_vulnerability,
      Bool_or(custom_permissions.admin_vulnerability) AS admin_vulnerability
  FROM (
      VALUES (60357594, ARRAY[60357594]::integer[]),
          (65094811, ARRAY[65094811]::integer[]),
          (60357923, ARRAY[60357923]::integer[]),
          (9970, ARRAY[9970]::integer[])) AS groups (id, traversal_ids),
      LATERAL (
  		(SELECT BOOL_OR(member_roles.read_vulnerability) AS read_vulnerability, BOOL_OR(member_roles.admin_vulnerability) AS admin_vulnerability
  		FROM members
  		LEFT OUTER JOIN member_roles ON member_roles.id = members.member_role_id
  		WHERE members.source_type = 'Namespace' AND "members"."user_id" = 11997412
  		AND groups.traversal_ids @> ARRAY[members.source_id]::int[]
  		AND (member_roles.read_vulnerability = TRUE OR member_roles.admin_vulnerability = TRUE))
  		UNION
  		(SELECT FALSE AS read_vulnerability, FALSE AS admin_vulnerability)
  	) AS custom_permissions
  GROUP BY groups.id

  which should do the same, but I find easier to read?