Link dataconnect package and add invoice hub

Wire up the dataconnect-generated package for the web app and add a new `hub` field to invoice mutations and queries. Updates include: add package links in apps/web package and workspace config, adjust connector.yaml JavaScript SDK output/package paths, add `hub` to invoice create/update mutations and to invoice queries, remove many example dataconnect GraphQL files and the web README, and minor formatting/newline fixes (Makefile and several .gql files).

backend/dataconnect/connector/connector.yaml

@@ -4,8 +4,8 @@ generate:
     - outputDir: ../../../apps/mobile/packages/data_connect/lib/src/dataconnect_generated
       package: dataconnect_generated/generated.dart
   javascriptSdk:
-    - outputDir: ..\..\..\apps\web\src\dataconnect-generated
-      package: "@dataconnect/generated"
-      packageJsonDir: ..\..\..\apps\web
-      react: true
+    - react: true
       angular: false
+      outputDir: ../../../apps/web/src/dataconnect-generated
+      package: "@dataconnect/generated"
+      packageJsonDir: ../../../apps/web