Lists users with pagination or searches for users matching a SCIM filter expression. When a filter is provided, it takes precedence and pagination parameters are ignored. Without a filter, returns a paginated list of all users for the tenant. Supported filter operators: eq on attributes userName, emails.value, externalId.
When no filter is provided and pagination parameters are omitted, defaults apply: startIndex defaults to 1 and count defaults to 100.
Pagination follows RFC 7644 §3.4.2.4: startIndex < 1 is clamped to 1, negative count is treated as 0, and count=0 returns totalResults without resources.