[SharePoint] Extend Metadata Indexing to custom one

[fred-maussion]

Problem Description

While connecting an Elastic Cloud Instance to a Sharepoint Online using Workplace search, we can only get defaut metadata and not the custom attached to the hosted documents.

Proposed Solution

As it's a pretty standard usage as many organization have their own metadata labels to add context to their documents, Sharepoint Online connector should be able to access and index the custom metada.

Alternatives

A workaround is possible by adapting the logic in the sharepoint online connector package but

1. customer will have to modify the connector either himself or through PS
2. deploy this modified version into a dedicated cloud VPS instance to keep the solution over the cloud which is against a move cloud full SaaS strategy
3. No support from us until the custom code has been merged to the main branch and accepted.

Additional Context

This affect our ESS product

[danajuratoni]

@fred-maussion

add context to their documents, Sharepoint Online connector should be able to access and index the custom metada.

Do you have insights what are customers usually defining custom metadata for? Which SharePoint entities(lists, lists items or files) are of interest to have custom metadata?
Specifying which objects are of interest would help a lot, since their ingestion would likely need to be individually handled for SPO.
cc: @artem-shelkovnikov