Feature/dsprotection

[pschuermann97]

Reason for this PR:

• implemented version 1 of double-spending protection service + wrote unit tests for handlers

Changes in this PR:

• handlers on DB side that provide functionality of double-spending protection service (see changelog for details)
• client-side request methods for the above functionality
• dbSync algo. implemented according to 2020 incentive system paper
• Link, Trace, VerifyDs implemented according to above paper
• minimal running example of deduct service implemented (see issue list for open problems)

Checklist:

Select whatever applies:

• [x] Test written
• [x] Code Properly Formatted
• [x] Documented
• [x] Changelog updated

[feidens]

How thorough should the review be?

[JanBobolz]

How thorough should the review be?

From the meeting: Only review if you want to. Also, I think we want to wait until merge conflicts have been solved.

[JanBobolz]

Rerequest review when conflicts have been solved.

[this-kramer]

Rerequest review when conflicts have been solved.

I think there will be a new PR anyways since @pschuermann97 moved to a new branch :+1: