Add Moodle data source integration (#11325)

### What problem does this PR solve?

This PR adds a native Moodle connector to sync content (courses,
resources, forums, assignments, pages, books) into RAGFlow.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

common/constants.py

@@ -118,6 +118,7 @@ class FileSource(StrEnum):
     SHAREPOINT = "sharepoint"
     SLACK = "slack"
     TEAMS = "teams"
+    MOODLE = "moodle"
 
 
 class PipelineTaskType(StrEnum):