Fix some OpenAPI issues (#970)

* Fix #933, update externals docs url to current version

* Fix #962, openApi don't err on nonexistent schema

* Fix #954, make OpenAPI rpc output dependent on user privileges

test/Feature/NonexistentSchemaSpec.hs

@@ -0,0 +1,15 @@
+module Feature.NonexistentSchemaSpec where
+
+import Network.Wai (Application)
+import Protolude hiding (get)
+import Test.Hspec
+import Test.Hspec.Wai
+
+spec :: SpecWith Application
+spec =
+  describe "Non existent api schema" $ do
+    it "succeeds when requesting root path" $
+      get "/" `shouldRespondWith` 200
+
+    it "gives 404 when requesting a nonexistent table in this nonexistent schema" $
+      get "/nonexistent_table" `shouldRespondWith` 404