Move release webhook to notification

[lunny]

As title.

[6543]

@lunny

mode, _ := models.AccessLevel(doer, rel.Repo)
	if err := webhook.PrepareWebhooks(rel.Repo, models.HookEventRelease, &api.ReleasePayload{
		Action:     api.HookReleaseUpdated,
		Release:    rel.APIFormat(),
		Repository: rel.Repo.APIFormat(mode),
		Sender:     doer.APIFormat(),
	}); err != nil {
		log.Error("PrepareWebhooks: %v", err)
	}

exists 3 times only differ in Action: xy

does it make sence to move this in a seperate function wich is used by all three funcitons?
or will it block later extentions?

[lunny]

@6543 done.

[6543]

CI.restart()

[techknowlogick]

restarted

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@6d42add). Click here to learn what that means.
The diff coverage is 56%.

@@            Coverage Diff            @@
##             master    #8817   +/-   ##
=========================================
  Coverage          ?   41.26%           
=========================================
  Files             ?      543           
  Lines             ?    69769           
  Branches          ?        0           
=========================================
  Hits              ?    28792           
  Misses            ?    37298           
  Partials          ?     3679

Impacted Files	Coverage Δ
modules/notification/webhook/webhook.go	40.18% <54.54%> (ø)
services/release/release.go	24.77% <66.66%> (ø)

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[6543]

@techknowlogick can you reviwe&merge?