feat(agent): add mediation and ability to send messages

[goncalo-frade-iohk]

Need to add tests but since it is already a quite large PR. I will initiate a draft PR.

[hamada147]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ KOTLIN	ktlint	90	7	0	194.42s
✅ REPOSITORY	checkov	yes		no	14.54s
✅ REPOSITORY	devskim	yes		no	0.97s
✅ REPOSITORY	dustilock	yes		no	0.02s
✅ REPOSITORY	git_diff	yes		no	0.02s
✅ REPOSITORY	secretlint	yes		no	1.78s
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✅ REPOSITORY	trivy	yes		no	4.08s

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[cristianIOHK]

Are we going to have multiple MediationHandler implementations? If not, why Basic instead of MediatorHandlerImpl?
Just curious, if I see Basic I would expect a Custom or Advanced or something more.

[hamada147]

It depends on @goncalo-frade-iohk answer.

[goncalo-frade-iohk]

Yeah we can change the name. This is basically an implementation we provide but the developer can provide any implementation that he desires.

[cristianIOHK]

I see. In that case in my opinion would make more sense to name it DefaultMediationHandler, if a user wants to use its own implementation fine, if not we have our default implementation.

[goncalo-frade-iohk]

Done

[cristianIOHK]

@goncalo-frade-iohk @hamada147 @elribonazo left a bunch of comments, would like your opinion on those.