Allow the dataset to generate users with a limited number of unique passwords

[ryanemerson]

Closes #1237

I have kept it simple for now and only reused credentials per create-users invocation. The reason for this is that the unique-credential-count ultimately determines the password, so storing and reloading the credentials in the DB means that we then need to handle unique-credential-count changing.

Passwords can be calcuated using: password-$(i % unique-credential-count) where i is the user number.

Quick local benchmark:

4s ./dataset/dataset-import.sh -a create-users -u 10000 -U 100 -l http://localhost:8080/realms/master/dataset

vs

45s ./dataset/dataset-import.sh -a create-users -u 10000 -l http://localhost:8080/realms/master/dataset

I haven't added any docs yet, as I wasn't sure if this was functionality we want to advertise or are happy keeping it hidden for our own needs. Let me know if we require docs.

[ahus1]

Thank you for the pull request, looks good to me.

+1 for adding a minimal set of docs. I think it will come in handy for those who want to test millions of users. It is open source, and we shouldn't hide this gem in the code but make it useful for everyone.

Would be updating Gatling be part if this issue, or a follow-up issue? I'm ok to make it a follow-up issue.

[ryanemerson]

I have added the docs and gatling benchmark logic, I also updated the keycloak-create-dataset workflow to include an input for this configuration.

I didn't update any of the benchmark workflows as they already have the max number of inputs (10) and I figured if we do want to execute these tests (semi-)regularly, we probably would have a dedicated cron workflow.

[pruivo]

LGTM. Tested the create-realm and benchmark run with 1 unique password, and it worked.
I'll let @ahus1 review the docs :)

[ahus1]

Thank you for the code changes and the docs. Approving!