Allow to disable digits in Faker::Internet.password method

[francktrouillez]

Motivation / Background

Currently, a digit is always added to the string generated by Faker::Interner.password. There's currently no way to disable this behavior.

Also, with the current behavior, running Faker::Internet.password(min_length: 2, max_length: 2, mix_case: true) will return a password of length 3, as a digit is always added to the string, in addition to the uppercase and lowercase letters.

Changes proposed in this pull request

This PR allows to disable the use of digits (and the auto-addition of one) when generating passwords. By default, a digit is added, but this can be disabled by setting the digits option to false. Also, when the digits option is set to true (current and default behavior), the required length of the password is updated to reflect the presence of the digit.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug, refactor something, or add a feature.
• Tests and Rubocop are passing before submitting your proposed changes.

If you're proposing a new generator or locale:

• [ ] Double-check the existing generators documentation to make sure the new generator you want to add doesn't already exist.
• [ ] You've reviewed and followed the Contributing guidelines.

Closing notes

I'm open to any feedback or suggestions on how to improve this PR if this idea makes sense.

Thank you very much!