Add submission blacklist

[biast12]

Adds the submission_blacklist table. The dashboard uses it to block users and servers from gallery submissions, and users from integration review. Also fixes the bot-wide blacklist queries hiding database errors.

• New SubmissionBlacklist table: feature, target_type, target_id, reason, primary key (feature, target_type, target_id).
  • Methods: IsBlacklisted (matches the user or the server, preferring the user), List, Add (an upsert of the reason) and Delete.
  • SubmissionFeature.AllowsTarget: gallery takes users and servers; integrations take users only.
  • Registered in Database/CreateTables and exempt from guild purge.
• Audit codes: actions 450/451 (add/remove) and resource 39.
• Fix: ServerBlacklist.ListAll, ServerBlacklist.ListAllEntries and GlobalBlacklist.ListAll now defer rows.Close() and return rows.Err(). On a warm connection, pgx reports query errors only through rows.Err(), so these returned an empty list with no error.
  • In the worker, the cache refresh then replaced the blacklist cache with that list, which unbanned everyone until the next refresh.
  • In the dashboard, the admin Server/Global Blacklist pages now show an error instead of an empty list.

SQL:

CREATE TABLE IF NOT EXISTS submission_blacklist(
      "feature" TEXT NOT NULL,
      "target_type" TEXT NOT NULL,
      "target_id" int8 NOT NULL,
      "reason" TEXT,
      PRIMARY KEY("feature", "target_type", "target_id")
);

For: TicketsBot-cloud/dashboard#153

Type of Change

• Bug fix
• New feature
• Breaking change

Checklist

• My code follows the style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works