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/data_source/config.py

@@ -48,6 +48,7 @@ class DocumentSource(str, Enum):
     GOOGLE_DRIVE = "google_drive"
     GMAIL = "gmail"
     DISCORD = "discord"
+    MOODLE = "moodle"
     S3_COMPATIBLE = "s3_compatible"