Do not allow underscore in baseName to prevent invalid hostnames

[josepaiva94]

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Fixes #417 with the suggested fix "Add error message when user tries to generate microservice with an underscore or illegal character according to URI spec in the service name."

However, i would like to use dashes. May I make another PR or is there a good reason against dashes in baseName?

[MathieuAA]

Hello, your fix disallow underscores for every type of app, not just MS. Yes, another PR for dashes if they are allowed.