mysql_grant doesn't detect external changes

[eraac]

Terraform Version

Terraform v0.12.20
+ provider.mysql v1.9.0

Affected Resource(s)

• mysql_grant

Expected Behavior

External/manual changes for privileges should be rollback with a terraform apply

Actual Behavior

External/manual changes aren't detected

Steps to Reproduce

Please list the steps required to reproduce the issue, for example:

1. terraform apply with mysql_grant
2. change from database (remove one privilege)
3. terraform apply don't detect change