feat: filter top-level resource with embed filter

This is enabled by adding `!inner` to the embedded resource

/projects?select=*,clients!inner(*)&clients.id=eq.12

This behaviour can be enabled by default with the config option

db-embed-default-join='inner'

Which saves the need for specifying `!inner` on every request.
If this is enabled, the previous behavior can be restored
per request by specifying `!left`  on the embedded resource.

/projects?select=*,clients!left(*)&clients.id=eq.12`

Tested on M20/02M/M2M relationships, views, RPC.

src/PostgREST/App.hs

@@ -572,7 +572,7 @@ returnsScalar _                   = False
 readRequest :: Monad m => QualifiedIdentifier -> RequestContext -> Handler m ReadRequest
 readRequest QualifiedIdentifier{..} (RequestContext AppConfig{..} dbStructure apiRequest _) =
   liftEither $
-    ReqBuilder.readRequest qiSchema qiName configDbMaxRows
+    ReqBuilder.readRequest qiSchema qiName configDbMaxRows configDbEmbedDefaultJoin
       (dbRelationships dbStructure)
       apiRequest