Cluster /{key}/docs endpoint for shareable Swagger UI. (#590)

add `/{key}/docs` for Modules. If there is no `openapi_spec` method or the module is not found, we see an error like so:

![image.png](https://graphite-user-uploaded-assets-prod.s3.amazonaws.com/O6PzvaCA4i9G3krtjvRT/f6b7cc21-6372-4e00-931c-fc8733360905.png)

runhouse/servers/http/http_server.py

@@ -14,6 +14,7 @@
 import yaml
 from fastapi import Body, FastAPI, HTTPException, Request
 from fastapi.encoders import jsonable_encoder
+from fastapi.openapi.docs import get_redoc_html, get_swagger_ui_html
 from fastapi.responses import StreamingResponse
 
 from runhouse.constants import (
@@ -47,6 +48,7 @@
 from runhouse.servers.obj_store import (
     ClusterServletSetupOption,
     ObjStore,
+    ObjStoreError,
     RaySetupOption,
 )
 
@@ -361,6 +363,45 @@ async def _call(
                 from_http_server=True,
             )
 
+    # Open API docs routes
+    @staticmethod
+    @app.get("/{key}/openapi.json")
+    @validate_cluster_access
+    async def get_openapi_spec(request: Request, key: str):
+        try:
+            module_openapi_spec = obj_store.call(
+                key, method_name="openapi_spec", serialization=None
+            )
+        except (AttributeError, ObjStoreError):
+            # The object put on the server is not an `rh.Module`, so it doesn't have an openapi_spec method
+            # OR
+            # The object is not found in the object store at all
+            module_openapi_spec = None
+
+        if not module_openapi_spec:
+            raise HTTPException(status_code=404, detail=f"Module {key} not found.")
+
+        return module_openapi_spec
+
+    @staticmethod
+    @app.get("/{key}/redoc")
+    @validate_cluster_access
+    async def get_redoc(request: Request, key: str):
+        return get_redoc_html(
+            openapi_url=f"/{key}/openapi.json", title="Developer Documentation"
+        )
+
+    @staticmethod
+    @app.get("/{key}/docs")
+    @validate_cluster_access
+    async def get_swagger_ui_html(request: Request, key: str):
+        return get_swagger_ui_html(
+            openapi_url=f"/{key}/openapi.json",
+            title=f"{key} - Swagger UI",
+            oauth2_redirect_url=app.swagger_ui_oauth2_redirect_url,
+            init_oauth=app.swagger_ui_init_oauth,
+        )
+
     # TODO match "/{key}/{method_name}/{path:more_path}" for asgi / proxy requests
     @staticmethod
     @app.post("/{key}/{method_name}")