chore: add prebuilds system user (#16916)

Pre-requisite for https://github.com/coder/coder/pull/16891

Closes https://github.com/coder/internal/issues/515

This PR introduces a new concept of a "system" user.

Our data model requires that all workspaces have an owner (a `users`
relation), and prebuilds is a feature that will spin up workspaces to be
claimed later by actual users - and thus needs to own the workspaces in
the interim.

Naturally, introducing a change like this touches a few aspects around
the codebase and we've taken the approach _default hidden_ here; in
other words, queries for users will by default _exclude_ all system
users, but there is a flag to ensure they can be displayed. This keeps
the changeset relatively small.

This user has minimal permissions (it's equivalent to a `member` since
it has no roles). It will be associated with the default org in the
initial migration, and thereafter we'll need to somehow ensure its
membership aligns with templates (which are org-scoped) for which it'll
need to provision prebuilds; that's a solution we'll have in a
subsequent PR.

---------

Signed-off-by: Danny Kopping <dannykopping@gmail.com>
Co-authored-by: Sas Swart <sas.swart.cdk@gmail.com>

coderd/database/migrations/000195_oauth2_provider_codes.up.sql

@@ -43,6 +43,10 @@ AFTER DELETE ON oauth2_provider_app_tokens
 FOR EACH ROW
 EXECUTE PROCEDURE delete_deleted_oauth2_provider_app_token_api_key();
 
+-- This migration has been modified after its initial commit.
+-- The new implementation makes the same changes as the original, but
+-- takes into account the message in create_migration.sh. This is done
+-- to allow the insertion of a user with the "none" login type in later migrations.
 CREATE TYPE new_logintype AS ENUM (
   'password',
   'github',

coderd/database/migrations/000308_system_user.down.sql

@@ -0,0 +1,50 @@
+DROP VIEW IF EXISTS group_members_expanded;
+CREATE VIEW group_members_expanded AS
+ WITH all_members AS (
+         SELECT group_members.user_id,
+            group_members.group_id
+           FROM group_members
+        UNION
+         SELECT organization_members.user_id,
+            organization_members.organization_id AS group_id
+           FROM organization_members
+        )
+ SELECT users.id AS user_id,
+    users.email AS user_email,
+    users.username AS user_username,
+    users.hashed_password AS user_hashed_password,
+    users.created_at AS user_created_at,
+    users.updated_at AS user_updated_at,
+    users.status AS user_status,
+    users.rbac_roles AS user_rbac_roles,
+    users.login_type AS user_login_type,
+    users.avatar_url AS user_avatar_url,
+    users.deleted AS user_deleted,
+    users.last_seen_at AS user_last_seen_at,
+    users.quiet_hours_schedule AS user_quiet_hours_schedule,
+    users.name AS user_name,
+    users.github_com_user_id AS user_github_com_user_id,
+    groups.organization_id,
+    groups.name AS group_name,
+    all_members.group_id
+   FROM ((all_members
+     JOIN users ON ((users.id = all_members.user_id)))
+     JOIN groups ON ((groups.id = all_members.group_id)))
+  WHERE (users.deleted = false);
+
+COMMENT ON VIEW group_members_expanded IS 'Joins group members with user information, organization ID, group name. Includes both regular group members and organization members (as part of the "Everyone" group).';
+
+-- Remove system user from organizations
+DELETE FROM organization_members
+WHERE user_id = 'c42fdf75-3097-471c-8c33-fb52454d81c0';
+
+-- Delete user status changes
+DELETE FROM user_status_changes
+WHERE user_id = 'c42fdf75-3097-471c-8c33-fb52454d81c0';
+
+-- Delete system user
+DELETE FROM users
+WHERE id = 'c42fdf75-3097-471c-8c33-fb52454d81c0';
+
+-- Drop column
+ALTER TABLE users DROP COLUMN IF EXISTS is_system;

coderd/database/migrations/000308_system_user.up.sql

@@ -0,0 +1,57 @@
+ALTER TABLE users
+	ADD COLUMN is_system bool DEFAULT false NOT NULL;
+
+COMMENT ON COLUMN users.is_system IS 'Determines if a user is a system user, and therefore cannot login or perform normal actions';
+
+INSERT INTO users (id, email, username, name, created_at, updated_at, status, rbac_roles, hashed_password, is_system, login_type)
+VALUES ('c42fdf75-3097-471c-8c33-fb52454d81c0', 'prebuilds@system', 'prebuilds', 'Prebuilds Owner', now(), now(),
+		'active', '{}', 'none', true, 'none'::login_type);
+
+DROP VIEW IF EXISTS group_members_expanded;
+CREATE VIEW group_members_expanded AS
+ WITH all_members AS (
+         SELECT group_members.user_id,
+            group_members.group_id
+           FROM group_members
+        UNION
+         SELECT organization_members.user_id,
+            organization_members.organization_id AS group_id
+           FROM organization_members
+        )
+ SELECT users.id AS user_id,
+    users.email AS user_email,
+    users.username AS user_username,
+    users.hashed_password AS user_hashed_password,
+    users.created_at AS user_created_at,
+    users.updated_at AS user_updated_at,
+    users.status AS user_status,
+    users.rbac_roles AS user_rbac_roles,
+    users.login_type AS user_login_type,
+    users.avatar_url AS user_avatar_url,
+    users.deleted AS user_deleted,
+    users.last_seen_at AS user_last_seen_at,
+    users.quiet_hours_schedule AS user_quiet_hours_schedule,
+    users.name AS user_name,
+    users.github_com_user_id AS user_github_com_user_id,
+    users.is_system AS user_is_system,
+    groups.organization_id,
+    groups.name AS group_name,
+    all_members.group_id
+   FROM ((all_members
+     JOIN users ON ((users.id = all_members.user_id)))
+     JOIN groups ON ((groups.id = all_members.group_id)))
+  WHERE (users.deleted = false);
+
+COMMENT ON VIEW group_members_expanded IS 'Joins group members with user information, organization ID, group name. Includes both regular group members and organization members (as part of the "Everyone" group).';
+-- TODO: do we *want* to use the default org here? how do we handle multi-org?
+WITH default_org AS (SELECT id
+					 FROM organizations
+					 WHERE is_default = true
+					 LIMIT 1)
+INSERT
+INTO organization_members (organization_id, user_id, created_at, updated_at)
+SELECT default_org.id,
+	   'c42fdf75-3097-471c-8c33-fb52454d81c0', -- The system user responsible for prebuilds.
+	   NOW(),
+	   NOW()
+FROM default_org;