Updated app to PHP7.3 min supported version, For php8 support

- Updated remaining dependancies
- Upped min versions used
- Updated GH actions to drop 7.2 and include 8.0
- Updated phpunit & tests to 9.x

.github/workflows/phpunit.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        php: [7.2, 7.3, 7.4]
+        php: [7.3, 7.4, 8.0]
     steps:
     - uses: actions/checkout@v1
 

.github/workflows/test-migrations.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        php: [7.2, 7.3, 7.4]
+        php: [7.3, 7.4, 8.0]
     steps:
       - uses: actions/checkout@v1