* feat: more user_migration stuff
* create script to move users by node directly
* moved old scripts to `old` directory (for historic reasons, as well as
possible future use)
* cleaned up README
* try to solve the `parent row` error
an intermittent error may be responsible from one of two things:
1) a transaction failure resulted in a premature add of the unique key
to the UC filter.
2) an internal spanner update error resulting from trying to write the
bso before the user_collection row was written.
* Added "fix_collections.sql" script to update collections table to add
well known collections for future rectification.
* returned collection name lookup
* add "--user" arg to set bso and user id
* add `--dryrun` mode
