Improve separation of Uvicorn and Gunicorn servers

- Make `process_manager` a required argument for `start.start_server()`
- Only set Gunicorn conf path when running Gunicorn

All unit tests pass, but when running Uvicorn, tests don't finish until
a manual keyboard interrupt is passed (`^C`). A context manager may be
needed to only run the server for a specified time.

```text
pytest
....................^C.^C.^C..........x.........                  [100%]
41 passed, 1 xfailed in 7.18s

pytest tests/test_start.py::TestStartServer::test_start_server_uvicorn \
  -vv
========================= test session starts =========================
platform darwin -- Python 3.8.5, pytest-6.0.1, py-1.9.0, pluggy-0.13.1
-- /Users/brendon/dev/inboard/.venv/bin/python3
cachedir: .pytest_cache
rootdir: /Users/brendon/dev/inboard, configfile: pyproject.toml
plugins: mock-3.3.1
collected 3 items

tests/test_start.py::TestStartServer::test_start_server_uvicorn[inboard
.app.base.main:app] ^CPASSED [ 33%]
tests/test_start.py::TestStartServer::test_start_server_uvicorn[inboard
.app.fastapibase.main:app] ^CPASSED [ 66%]
tests/test_start.py::TestStartServer::test_start_server_uvicorn[inboard
.app.starlettebase.main:app] ^CPASSED [100%]

========================== 3 passed in 9.96s ==========================
```

inboard/start.py

@@ -93,21 +93,18 @@ def run_pre_start_script(logger: Logger = logging.getLogger()) -> str:
 
 
 def start_server(
+    process_manager: str,
     app_module: str = str(os.getenv("APP_MODULE", "inboard.app.base.main:app")),
-    gunicorn_conf: str = str(
-        os.getenv("GUNICORN_CONF", "/app/inboard/gunicorn_conf.py")
-    ),
     logger: Logger = logging.getLogger(),
     logging_conf_dict: Dict[str, Any] = None,
-    process_manager: str = str(os.getenv("PROCESS_MANAGER", "gunicorn")),
     with_reload: bool = bool(os.getenv("WITH_RELOAD", False)),
     worker_class: str = str(os.getenv("WORKER_CLASS", "uvicorn.workers.UvicornWorker")),
 ) -> None:
     """Start the Uvicorn or Gunicorn server."""
     try:
         if process_manager == "gunicorn":
             logger.debug("Running Uvicorn with Gunicorn.")
-            gunicorn_conf_path = Path(gunicorn_conf)
+            gunicorn_conf_path = set_conf_path("gunicorn")
             subprocess.run(
                 ["gunicorn", "-k", worker_class, "-c", gunicorn_conf_path, app_module]
             )
@@ -131,12 +128,11 @@ def start_server(
 if __name__ == "__main__":
     logger = logging.getLogger()
     logging_conf_dict = configure_logging(logger=logger)
-    gunicorn_conf_path = set_conf_path("gunicorn")
     app_module = set_app_module(logger=logger)
     run_pre_start_script(logger=logger)
     start_server(
+        str(os.getenv("PROCESS_MANAGER", "gunicorn")),
         app_module=app_module,
-        gunicorn_conf=gunicorn_conf_path,
         logger=logger,
         logging_conf_dict=logging_conf_dict,
     )

tests/test_start.py

@@ -330,7 +330,6 @@ class TestStartServer:
     def test_start_server_uvicorn(
         self,
         app_module: str,
-        gunicorn_conf_path: Path,
         logging_conf_dict: Dict[str, Any],
         mock_logger: logging.Logger,
         mocker: MockerFixture,
@@ -340,14 +339,17 @@ def test_start_server_uvicorn(
         monkeypatch.setenv("LOG_FORMAT", "uvicorn")
         monkeypatch.setenv("LOG_LEVEL", "debug")
         monkeypatch.setenv("PROCESS_MANAGER", "uvicorn")
+        assert os.getenv("LOG_FORMAT") == "uvicorn"
+        assert os.getenv("LOG_LEVEL") == "debug"
+        assert os.getenv("PROCESS_MANAGER") == "uvicorn"
+        # TODO: need to send interrupt to stop server. Try with a context manager?
         start.start_server(
+            str(os.getenv("PROCESS_MANAGER")),
             app_module=app_module,
-            gunicorn_conf=str(gunicorn_conf_path),
             logger=mock_logger,
             logging_conf_dict=logging_conf_dict,
-            with_reload=False,
         )
-        mock_logger.debug.assert_called_once_with("Running Uvicorn with Gunicorn.")  # type: ignore[attr-defined]  # noqa: E501
+        mock_logger.debug.assert_called_once_with("Running Uvicorn without Gunicorn.")  # type: ignore[attr-defined]  # noqa: E501
 
     @pytest.mark.parametrize(
         "app_module",
@@ -367,20 +369,23 @@ def test_start_server_uvicorn_gunicorn(
         monkeypatch: MonkeyPatch,
     ) -> None:
         """Test `start.start_server` with Uvicorn managed by Gunicorn."""
+        assert os.getenv("GUNICORN_CONF", str(gunicorn_conf_path))
         monkeypatch.setenv("LOG_FORMAT", "gunicorn")
         monkeypatch.setenv("LOG_LEVEL", "debug")
         monkeypatch.setenv("PROCESS_MANAGER", "gunicorn")
+        assert os.getenv("LOG_FORMAT") == "gunicorn"
+        assert os.getenv("LOG_LEVEL") == "debug"
+        assert os.getenv("PROCESS_MANAGER") == "gunicorn"
         start.start_server(
+            str(os.getenv("PROCESS_MANAGER")),
             app_module=app_module,
-            gunicorn_conf=str(gunicorn_conf_path),
             logger=mock_logger,
             logging_conf_dict=logging_conf_dict,
         )
         mock_logger.debug.assert_called_once_with("Running Uvicorn with Gunicorn.")  # type: ignore[attr-defined]  # noqa: E501
 
     def test_start_server_uvicorn_incorrect_module(
         self,
-        gunicorn_conf_path: Path,
         logging_conf_dict: Dict[str, Any],
         mock_logger: logging.Logger,
         mocker: MockerFixture,
@@ -391,11 +396,10 @@ def test_start_server_uvicorn_incorrect_module(
             monkeypatch.setenv("LOG_LEVEL", "debug")
             monkeypatch.setenv("WITH_RELOAD", "false")
             start.start_server(
+                "uvicorn",
                 app_module="incorrect.base.main:app",
-                gunicorn_conf=str(gunicorn_conf_path),
                 logger=mock_logger,
                 logging_conf_dict=logging_conf_dict,
-                process_manager="uvicorn",
             )
             logger_error_msg = "Error when starting server with start script:"
             module_error_msg = "No module named incorrect.base.main:app"
@@ -428,11 +432,10 @@ def test_start_server_uvicorn_incorrect_process_manager(
             monkeypatch.setenv("LOG_LEVEL", "debug")
             monkeypatch.setenv("WITH_RELOAD", "false")
             start.start_server(
+                "incorrect",
                 app_module=app_module,
-                gunicorn_conf=str(gunicorn_conf_path),
                 logger=mock_logger,
                 logging_conf_dict=logging_conf_dict,
-                process_manager="incorrect",
             )
             logger_error_msg = "Error when starting server with start script:"
             process_error_msg = (