Wrong username when the project name is > 1 word

[samkahchiin]

      let [project, env] = i.DBInstanceIdentifier.split('-')

      let username = env ? `${project}_${env}_readonly` : '-'

Currently, the apps expect the project name will only consist of one word, if it is more than one word, it will generate the wrong db username

eg. if the db identifier name is google-drive-staging,

it will thought the project name is google, and env name is drive
therefore the username will be
google_drive_readonly

but the user would expect the username to be
google_drive_staging_readonly

https://github.com/dbl-works/rds-manager/blob/d8cb34dc0d75fe593ceed16ba3e63d59782831ac/src/renderer/rds_manager.js#L18

[swiknaba]

to test if this is still an issue in the Rust rewrite, or if that was a bug in the previous JS version.