Allow deleting Organizations (team sites) through the Rest API

[fflorent]

Describe the problem to be solved

One of our users wants to delete an organization.

Currently, AFAIK, no option can be offered to delete this resource.

Describe the solution you would like

Add an endpoint DELETE /orgs/{orgId}, so there is at least a possibility for advanced users and/or admin to delete organizations.

EDIT: Ah, right, I found the API endpoint exist! https://github.com/gristlabs/grist-core/blob/bbb9071175616890848993b85413de6b044b4052/app/gen-server/ApiServer.ts#L183-L187

It just misses a documentation.