Add PocketBase client with contracts and containerized tests

Directory.Packages.props

@@ -18,6 +18,7 @@
         <PackageVersion Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.12" />
         <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
         <PackageVersion Include="Shouldly" Version="4.3.0" />
+        <PackageVersion Include="Testcontainers" Version="4.15.0" />
         <PackageVersion Include="xunit" Version="2.9.3" />
         <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.4" />
     </ItemGroup>