Regex to parse a SHOW GRANTS line. Inspired by several stack overflow posts and
adjusted to account for the different quoting styles across MySQL versions.
If this regex matches then this is a grant on an actual object which looks like:
GRANT SELECT, INSERT, UPDATE ON db1.* TO u1@localhost
GRANT SELECT ON db1.table1 TO my_user@localhost WITH GRANT OPTION
The regex needs to account for the possibility of a wildcard schema or table, and for the
quote-char to be part of the table/schema name too.
Group 1 is the list of privileges being granted
Group 2 is either the wildcard * or a quoted database/schema
Group 4 is the unquoted database/schema when the wildcard is not matched
Group 5 is either the wildcard * or a quoted table
Group 7 is the unquoted table when the wildcard is not matched
Group 9 is the user being granted
We use the fancy_regex crate to allow backreferences which are necessary to find the ending
quote of each identifier since there are different quoting types across mysql versions.