refactor: migrate from deprecated database manager

Changes:
- Swaps out `SingleConnectionDatabaseManager` to `DatabaseManager`
  across the repo.
- Updates `backend-test-utils` to generate test plugin names prefixed
  with db to satisfy plugin naming constraint, e.g. 0 becomes db0.

Signed-off-by: Minn Soe <contributions@minn.io>

plugins/code-coverage-backend/src/service/CodeCoverageDatabase.test.ts

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { SingleConnectionDatabaseManager } from '@backstage/backend-common';
+import { DatabaseManager } from '@backstage/backend-common';
 import { stringifyEntityRef } from '@backstage/catalog-model';
 import { ConfigReader } from '@backstage/config';
 import {
@@ -22,7 +22,7 @@ import {
 } from './CodeCoverageDatabase';
 import { JsonCodeCoverage } from './types';
 
-const db = SingleConnectionDatabaseManager.fromConfig(
+const db = DatabaseManager.fromConfig(
   new ConfigReader({
     backend: {
       database: {

plugins/code-coverage-backend/src/service/router.test.ts

@@ -20,14 +20,14 @@ import {
   getVoidLogger,
   PluginDatabaseManager,
   PluginEndpointDiscovery,
-  SingleConnectionDatabaseManager,
+  DatabaseManager,
   UrlReaders,
 } from '@backstage/backend-common';
 import { ConfigReader } from '@backstage/config';
 import { createRouter } from './router';
 
 function createDatabase(): PluginDatabaseManager {
-  return SingleConnectionDatabaseManager.fromConfig(
+  return DatabaseManager.fromConfig(
     new ConfigReader({
       backend: {
         database: {

plugins/scaffolder-backend/src/scaffolder/tasks/StorageTaskBroker.test.ts

@@ -14,17 +14,14 @@
  * limitations under the License.
  */
 
-import {
-  getVoidLogger,
-  SingleConnectionDatabaseManager,
-} from '@backstage/backend-common';
+import { getVoidLogger, DatabaseManager } from '@backstage/backend-common';
 import { ConfigReader } from '@backstage/config';
 import { DatabaseTaskStore } from './DatabaseTaskStore';
 import { StorageTaskBroker, TaskAgent } from './StorageTaskBroker';
 import { TaskSecrets, TaskSpec, DbTaskEventRow } from './types';
 
 async function createStore(): Promise<DatabaseTaskStore> {
-  const manager = SingleConnectionDatabaseManager.fromConfig(
+  const manager = DatabaseManager.fromConfig(
     new ConfigReader({
       backend: {
         database: {

plugins/scaffolder-backend/src/scaffolder/tasks/TaskWorker.test.ts

@@ -14,12 +14,9 @@
  * limitations under the License.
  */
 
-import {
-  getVoidLogger,
-  SingleConnectionDatabaseManager,
-} from '@backstage/backend-common';
-import { ConfigReader, JsonObject } from '@backstage/config';
 import os from 'os';
+import { getVoidLogger, DatabaseManager } from '@backstage/backend-common';
+import { ConfigReader, JsonObject } from '@backstage/config';
 import { createTemplateAction, TemplateActionRegistry } from '../actions';
 import { RepoSpec } from '../actions/builtin/publish/util';
 import { DatabaseTaskStore } from './DatabaseTaskStore';
@@ -27,7 +24,7 @@ import { StorageTaskBroker } from './StorageTaskBroker';
 import { TaskWorker } from './TaskWorker';
 
 async function createStore(): Promise<DatabaseTaskStore> {
-  const manager = SingleConnectionDatabaseManager.fromConfig(
+  const manager = DatabaseManager.fromConfig(
     new ConfigReader({
       backend: {
         database: {

plugins/scaffolder-backend/src/service/router.test.ts

@@ -31,7 +31,7 @@ jest.doMock('fs-extra', () => ({
 import {
   getVoidLogger,
   PluginDatabaseManager,
-  SingleConnectionDatabaseManager,
+  DatabaseManager,
   UrlReaders,
 } from '@backstage/backend-common';
 import { CatalogApi } from '@backstage/catalog-client';
@@ -47,7 +47,7 @@ const createCatalogClient = (templates: any[] = []) =>
   } as CatalogApi);
 
 function createDatabase(): PluginDatabaseManager {
-  return SingleConnectionDatabaseManager.fromConfig(
+  return DatabaseManager.fromConfig(
     new ConfigReader({
       backend: {
         database: {