Calculates unique maintainers for a workspace based on EventLog.

Maintainers are users who have successfully created or updated:

• Sections belonging to workspace versions of the workspace
• Notes belonging to sections of the workspace

Returns a map with:

• count - number of unique maintainers, at most 100
• maintainers - list of %{"user_id", "email", "name"}: the 100 who wrote most recently, listed by "name", then "user_id"

"email" is the address when the reader may see it — a master sees everyone's, a site user its own site's — and nil otherwise. "name" is what a screen shows: the email, "Master" for a master, "Unknown" for anyone else (MishkaCmsCore.Accounts.Helper.who/4). Neither which maintainers are listed nor their order depends on an address the reader does not see.

Uses raw SQL for performance with large datasets.