Decoupled notification service

[juherr]

The objective of having a decoupled notification service is to allow adding some other notification service (ie: a SlackNotificationService) without any change in the business code.

[goekay]

thanks @juherr!

[juherr]

@goekay thank for the merge. I didn't test the change very well and didn't check if unit tests are already covering the feature.
Please, tell me if I can improve it.

I will propose some other changes about notifications soon What is your favorite process? Is draft a good way for you to discuss about changes?

[goekay]

I didn't test the change very well and didn't check if unit tests are already covering the feature. Please, tell me if I can improve it.

i think the changes of this PR were straightforward and simple enough not to require tests. but usually, yeah, the more tests the better. you can keep that for future in mind. i am also trying to improve the situation when i add/change something.

I will propose some other changes about notifications soon What is your favorite process? Is draft a good way for you to discuss about changes?

i don't have a process. you can make a PR and we can discuss it as part of the review. or, if you want to discuss the idea without the actual effort of executing the idea, we can use an issue.