UTF-related errors in OCM invite manager

[glpatcern]

Seen with PSNC while testing the ScienceMesh setup, where the username was sso-0d6c2c87-3da4-44d9-9acd-35a85290992c:

 ERR home/reva/internal/grpc/services/ocminvitemanager/ocminvitemanager.go:197 > internal error: {
  "code": "SERVER_ERROR",
  "message": "unexpected error: Error 3988 (HY000): Conversion from collation utf8mb4_general_ci into latin1_swedish_ci impossible for parameter"
} error="internal error: {\n  \"code\": \"SERVER_ERROR\",\n  \"message\": \"unexpected error: Error 3988 (HY000): Conversion from collation utf8mb4_general_ci into latin1_swedish_ci impossible for parameter\"\n}" pid=1 traceid=0fd9b634bab470e39f95dea8ddaa9a97