pin fastapi to previous version

[vincentsarago]

first reported in developmentseed/geojson-pydantic#42

Here is what we get when requesting /docs

...
  File "/usr/local/lib/python3.8/site-packages/fastapi/openapi/utils.py", line 410, in get_openapi
    return jsonable_encoder(OpenAPI(**output), by_alias=True, exclude_none=True)  # type: ignore
  File "pydantic/main.py", line 406, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 21 validation errors for OpenAPI
components -> schemas -> LineString -> properties -> coordinates -> items -> anyOf -> 0 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> LineString -> properties -> coordinates -> items -> anyOf -> 1 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> LineString -> $ref
  field required (type=value_error.missing)
components -> schemas -> MultiLineString -> properties -> coordinates -> items -> items -> anyOf -> 0 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> MultiLineString -> properties -> coordinates -> items -> items -> anyOf -> 1 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> MultiLineString -> $ref
  field required (type=value_error.missing)
components -> schemas -> MultiPoint -> properties -> coordinates -> items -> anyOf -> 0 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> MultiPoint -> properties -> coordinates -> items -> anyOf -> 1 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> MultiPoint -> $ref
  field required (type=value_error.missing)
components -> schemas -> MultiPolygon -> properties -> coordinates -> items -> items -> items -> anyOf -> 0 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> MultiPolygon -> properties -> coordinates -> items -> items -> items -> anyOf -> 1 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> MultiPolygon -> $ref
  field required (type=value_error.missing)
components -> schemas -> PgstacSearch -> properties -> bbox -> anyOf -> 0 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> PgstacSearch -> properties -> bbox -> anyOf -> 1 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> PgstacSearch -> $ref
  field required (type=value_error.missing)
components -> schemas -> Point -> properties -> coordinates -> anyOf -> 0 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> Point -> properties -> coordinates -> anyOf -> 1 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> Point -> $ref
  field required (type=value_error.missing)
components -> schemas -> Polygon -> properties -> coordinates -> items -> items -> anyOf -> 0 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> Polygon -> properties -> coordinates -> items -> items -> anyOf -> 1 -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> Polygon -> $ref
  field required (type=value_error.missing)
...

As mentioned in the geojson-pydantic issue, the latest version of fastapi doesn't support Tuple with fixed size (work is ongoing to change this but not yet merged). While it worked with earlier fastapi version (0.65.1), the schema is not well representer (e.g for center: Optional[Tuple[float, float, int]] the openapi schema cannot render it but at least docs are shown 🤷‍♂️)

I'm not 100% sure which is the best version to use so it will need a closer look