Allow removing transaction extension endpoints from API docs

[geospatial-jeff]

Users may want to differentiate between read/write access and hiding the write endpoints from API docs helps with this.

[keul]

@geospatial-jeff in our application which instantiate a custom Client, we are removing stuff don't implemented in this way:

app = api.app

def catalogue_openapi() -> dict[str, Any]:
    """OpenAPI, but with not implemented paths removed."""
    del openapi_schema["paths"]["/collections/{collection_id}/items"]
    del openapi_schema["paths"]["/collections/{collection_id}/items/{item_id}"]
    del openapi_schema["paths"]["/search"]

    return openapi_schema

app.openapi = catalogue_openapi