chore(docs): Update quick start examples to match automatic generated password

[vax-r]

Summary

Currently Iggy support automatically generated password for default root user "iggy" when no custom root user credential is provided. Update README so users will know they need to set their own custom root user credentials with environment variables, and iggy's command will not success when providing "-u iggy -p iggy" if users didn't set it explicitly.

[spetz]

I think it might be worth adding that you can also start the Iggy server with an optional --with-default-root-credentials arg to have the default credentials set during the initial run.

[vax-r]

I think it might be worth adding that you can also start the Iggy server with an optional --with-default-root-credentials arg to have the default credentials set during the initial run.

Sure thing, I'm adding it now, though I see --with-default-root-credentials should better be set in development environment rather than production environment. Should I add the note ,too ?

[spetz]

I think it might be worth adding that you can also start the Iggy server with an optional --with-default-root-credentials arg to have the default credentials set during the initial run.

Sure thing, I'm adding it now, though I see --with-default-root-credentials should better be set in development environment rather than production environment. Should I add the note ,too ?

Yes, it's mostly a convenient way of starting the server with the default credentials (e.g. for the testing purposes) without a need to set the custom envs.