Add KS validation on ingested XML via drop folder
1. Add new configuration fields in XML drop folder the enable KS
validation.
2. If KS validation enabled enforce KS user and expiry validation in
ingestion process.
Changes after review
1. Add ability to override KS validation when providing Admin KS in the
ingestion XML.
2. If no user is located inside the item element and the session type is
user, take the user from the KS instead of failing the item upload.
Merge pull request #1792 from kaltura/IX-9.19.6-PLAT-1978

Add KS validation on ingested XML via drop folder