Update to FastAPI 0.104

This commit will update/upgrade to
[FastAPI 0.104](https://fastapi.tiangolo.com/release-notes/).

FastAPI 0.104 drops support for Python 3.7 and adds API reference docs
available [here](https://fastapi.tiangolo.com/reference/).

pyproject.toml

@@ -43,7 +43,7 @@ docs = [
   "mkdocs-material>=9,<10",
 ]
 fastapi = [
-  "fastapi>=0.103,<0.104",
+  "fastapi>=0.104,<0.105",
 ]
 starlette = [
   "starlette>=0.27,<0.28",