add starlette as a direct dependency

It was already an indirect dependency and already imported directly in
 a few places, but we should make that explicit.

pyproject.toml

@@ -32,6 +32,7 @@ dependencies = [
     "pyyaml",
     "rohmu >= 2.2.0",
     "sentry-sdk",
+    "starlette",
     "tabulate",
     "typing-extensions >= 4.7.1; python_version < '3.12'",
     "uvicorn",
@@ -59,6 +60,7 @@ f38 = [
     "pydantic == 1.10.2",
     "pyyaml == 6.0.0",
     "requests == 2.28.2",
+    "starlette == 0.27.0",
     "tabulate == 0.9.0",
     "uritemplate == 4.1.1",
     "urllib3 == 1.26.18",
@@ -81,6 +83,7 @@ f39 = [
     "pydantic == 1.10.14",
     "pyyaml == 6.0.1",
     "requests == 2.28.2",
+    "starlette == 0.27.0",
     "tabulate == 0.9.0",
     "uritemplate == 4.1.1",
     "urllib3 == 1.26.18",