use custom docker build to set max_locks_per_transaction for postgres

.github/workflows/test_docker.yml

@@ -0,0 +1,23 @@
+---
+name: Build docker image for testing code
+
+on:
+  push:
+    branches: [dev]
+  pull_request:
+    branches: [dev]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v3
+
+    - name: Build and push Docker image
+      uses: docker/build-push-action@v2
+      with:
+        context: .
+        push: true
+        tags: docker.pkg.github.com/edwardchalstrey1/seshat/tests-image:latest

.github/workflows/tests.yml

@@ -1,11 +1,12 @@
 ---
 name: Test code
 
+# Triggers the workflow on push or pull request to dev branch, see test_docker.yml
 on:
-  push:
-    branches: [dev]
-  pull_request:
-    branches: [dev]
+  workflow_run:
+    workflows: ["Build docker image for testing code"]
+    types:
+      - completed
 
 jobs:
   test_core:
@@ -16,7 +17,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     services:
       postgres:
-        image: postgis/postgis
+        image: docker.pkg.github.com/edwardchalstrey1/seshat/tests-image:latest
         env:
           POSTGRES_USER: postgres
           POSTGRES_PASSWORD: postgres

Dockerfile

@@ -0,0 +1,2 @@
+FROM postgis/postgis
+RUN echo "max_locks_per_transaction = 256" >> /var/lib/postgresql/data/postgresql.conf