Update postgres Docker tag to v15

.gitlab-ci.yml

@@ -55,7 +55,7 @@ pip:
 test_python:
   extends: .python_test_template
   services:
-    - postgres:14-alpine
+    - postgres:15-alpine
   variables:
     POSTGRES_HOST_AUTH_METHOD: trust
     DATABASE_URL: postgres://postgres@postgres/postgres

docker/dev/docker-compose.yml

@@ -23,7 +23,7 @@ services:
     image: redis:6-alpine
 
   db:
-    image: postgres:14-alpine
+    image: postgres:15-alpine
     environment:
       - POSTGRES_PASSWORD=website
       - POSTGRES_USER=website