fix(endpoints): do not reset organization's secrets when an endpoint is created or updated

[sranka]

Closes #19081

This PR fixes the endpoint service so that it does not reset all organization secrets when a notification endpoint is created or updated. SecretService.PutSecrets call, which that "deletes" all existing secrets, is replaced by PatchSecrets herein. A new test was added.

• CHANGELOG.md updated with a link to the PR (not the Issue)
• Well-formatted commit messages
• Rebased/mergeable
• Tests pass
• Signed CLA (if not already signed)

[sranka]

There is a good test that explains the semantics of PutSecrets. It would be IMHO even better to rename the SecretService's PutSecrets method to ResetSecrets to clearly indicate that all existing secrets are deleted and the new are set. I can offer this refactoring upon reviewer's request, it might be opinionated.

I guess that every code that now uses PutSecrets is suspicious to do the same mistake. I found also

influxdb/pkger/service.go

Lines 2424 to 2426 in 88cdf43

	createFn := func(ctx context.Context, i int, orgID, userID influxdb.ID) *applyErrBody {
	err := s.secretSVC.PutSecrets(ctx, orgID, secrets)
	if err != nil {

It should probably use PatchSecrets, @jsteenb2 ?

[glinton]

Can you add tests to show the old/new behavior

[sranka]

@glinton .. a test was added herein to validate the correct behavior