Add password reset feature

[mattlindsey]

I never added this because it requires an email delivery service and I was trying to keep the app's dependencies as limited as possible to make it really easy to deploy and get started.

Awhile ago I solved this in another rails app by using:

      config.action_mailer.delivery_method = :smtp
      config.action_mailer.smtp_settings = {
        address: "smtp.gmail.com",
        port: 587,
        domain: "gmail.com",
        user_name: Rails.application.credentials.dig(:gmail, :username),
        password: Rails.application.credentials.dig(:gmail, :password),
        authentication: :plain,
        enable_starttls_auto: true
      }
    end

And then configuring my personal gmail account to support SMTP delivery (I remember this was a little tricky but I found some special gmail help doc that explained how to do it).

This is probably the easiest for limited outbound email delivery. We could put it behind a feature flag and explain it in the README.

Originally posted by @krschacht in #703 (comment)

P.S. Add instruction on how to reset it to those with rails console access.

[mattlindsey]

If password reset by email doesn't work easily, an easy to deploy (behind a feature flag and in the README) would be an old fashioned question/answer reset (without new gem or email service dependencies).

I.e., A few questions like 'What is your mother's maiden name?' or better yet let the user write their own question.

[mattlindsey]

Just realized there are security issues with how passwords are reset, so nothing should be installed without proper review.