Feature request: Exclude connectors

[jonathanlukas]

Is your feature request related to a problem? Please describe.

When using the mail connector, I want to limit the interaction possibilities with my mail server.

Describe the solution you'd like

A way to include/exclude connectors.

Describe alternatives you've considered

Use them as they are and handle exceptions popping up.

Additional context

Follow-up to #127

[amardeep2006]

@jonathanlukas I have some idea . Can you have a look at this PR .

#182

This changes the default behavior and Mail Service will be disabled by default. However I have small doubt why we need to set both properties to true to enable it ?

       camunda.bpm.plugin.mail.notification.enabled: true
       camunda.bpm.plugin.mail.mail.notification.enabled: true

I need the background for two similar properties .
Open for suggestions.