add integration tests for postgresql, mysql and mariadb using testcontainers

commafeed-server/src/test/resources/config.test.yml

@@ -117,6 +117,9 @@ database:
   properties:
     charSet: UTF-8
   validationQuery: "/* CommaFeed Health Check */ SELECT 1"
+  minSize: 1
+  maxSize: 5
+  initialSize: 1
 
 server:
   applicationConnectors:

commafeed-server/src/test/resources/docker-images.properties

@@ -0,0 +1,3 @@
+postgresql=postgres:${postgresql.image.version}
+mysql=mysql:${mysql.image.version}
+mariadb=mariadb:${mariadb.image.version}