Add repo tests and fix build

.github/workflows/build-test.yml

@@ -0,0 +1,44 @@
+name: Build & Test
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 30
+
+    steps:
+      - uses: actions/checkout@v4.2.2
+        with:
+          submodules: recursive
+
+      - name: Setup .NET Core
+        uses: actions/setup-dotnet@v4.1.0
+        with:
+          dotnet-version: 10.0.x
+
+      - name: Install dependencies
+        run: dotnet restore
+
+      - name: Build
+        run: dotnet build --no-restore /p:WarningsAsErrors=nullable
+
+      - name: Run tests
+        shell: pwsh
+        run: dotnet test --no-build Content.Tests/Content.Tests.csproj -- NUnit.ConsoleOut=0 NUnit.TestOutputXml="logs" NUnit.WorkDirectory="$(pwd)/test_results"
+
+      - name: Archive NUnit3 test results.
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: nunit3-results-${{ matrix.os }}
+          path: test_results/*
+          retention-days: 7