Add pipeline commands (e.g. `Run DB Migrations`, `Run Tests`)

## Current Gap Example Adding a database to an application is really smooth with Qovery, but the database isn't functionally useful until I can set up the schema for it, generally by applying db migrations. In my case, I have a .NET app that uses entity framework as an ORM and can easily apply migrations with a `dotnet ef database update` command, but there's not a smooth process for doing that right now. Generally this might be in my pipeline with something like the below in CodeBuild. ```yaml version: 0.2 env: parameter-store: DOCKER_USERNAME: "/global/docker_username" DOCKER_PASSWORD: "/global/docker_password" NUGET_TOKEN: "/global/github_pat" DB_URL: "/global/myapp_db_url_$ENV" phases: install: commands: # Dotnet until it's a valid runtime - /usr/local/bin/dotnet-install.sh --channel LTS # runtime-versions: # dotnet: 5.0 pre_build: commands: - dotnet tool install --global dotnet-ef - export NUGET_USER=githubdeploy-myorg build: commands: - cd MyApp/src/MyApp - dotnet ef database update post_build: commands: - echo "Done" ``` ## Feature Request Regardless, it would be great if we had the option to add build steps like applying database migrations or running tests