feat: enable soft delete for organizations (#16584)

- Add deleted column to organizations table
- Add trigger to check for existing workspaces, templates, groups and
members in a org before allowing the soft delete

---------

Co-authored-by: Steven Masley <stevenmasley@gmail.com>
Co-authored-by: Steven Masley <Emyrk@users.noreply.github.com>

coderd/database/migrations/000296_organization_soft_delete.up.sql

@@ -0,0 +1,85 @@
+ALTER TABLE organizations ADD COLUMN deleted boolean DEFAULT FALSE NOT NULL;
+
+DROP INDEX IF EXISTS idx_organization_name;
+DROP INDEX IF EXISTS idx_organization_name_lower;
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_organization_name_lower ON organizations USING btree (lower(name))
+	where deleted = false;
+
+ALTER TABLE ONLY organizations
+	DROP CONSTRAINT IF EXISTS organizations_name;
+
+CREATE FUNCTION protect_deleting_organizations()
+	RETURNS TRIGGER AS
+$$
+DECLARE
+    workspace_count int;
+	template_count int;
+	group_count int;
+	member_count int;
+	provisioner_keys_count int;
+BEGIN
+    workspace_count := (
+        SELECT count(*) as count FROM workspaces
+        WHERE
+            workspaces.organization_id = OLD.id
+            AND workspaces.deleted = false
+    );
+
+	template_count := (
+        SELECT count(*) as count FROM templates
+        WHERE
+            templates.organization_id = OLD.id
+            AND templates.deleted = false
+    );
+
+	group_count := (
+        SELECT count(*) as count FROM groups
+        WHERE
+            groups.organization_id = OLD.id
+    );
+
+	member_count := (
+        SELECT count(*) as count FROM organization_members
+        WHERE
+            organization_members.organization_id = OLD.id
+    );
+
+	provisioner_keys_count := (
+		Select count(*) as count FROM provisioner_keys
+		WHERE
+			provisioner_keys.organization_id = OLD.id
+	);
+
+    -- Fail the deletion if one of the following:
+    -- * the organization has 1 or more workspaces
+	-- * the organization has 1 or more templates
+	-- * the organization has 1 or more groups other than "Everyone" group
+	-- * the organization has 1 or more members other than the organization owner
+	-- * the organization has 1 or more provisioner keys
+
+    IF (workspace_count + template_count + provisioner_keys_count) > 0 THEN
+            RAISE EXCEPTION 'cannot delete organization: organization has % workspaces, % templates, and % provisioner keys that must be deleted first', workspace_count, template_count, provisioner_keys_count;
+    END IF;
+
+	IF (group_count) > 1 THEN
+            RAISE EXCEPTION 'cannot delete organization: organization has % groups that must be deleted first', group_count - 1;
+    END IF;
+
+    -- Allow 1 member to exist, because you cannot remove yourself. You can
+    -- remove everyone else. Ideally, we only omit the member that matches
+    -- the user_id of the caller, however in a trigger, the caller is unknown.
+	IF (member_count) > 1 THEN
+            RAISE EXCEPTION 'cannot delete organization: organization has % members that must be deleted first', member_count - 1;
+    END IF;
+
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Trigger to protect organizations from being soft deleted with existing resources
+CREATE TRIGGER protect_deleting_organizations
+    BEFORE UPDATE ON organizations
+    FOR EACH ROW
+	WHEN (NEW.deleted = true AND OLD.deleted = false)
+    EXECUTE FUNCTION protect_deleting_organizations();