[fix][hooks] keep app credentials out of the effect payload (24.05)

[ar2rsawseen]

Backport of #7941 to release.24.05.

No test here: this branch's hooks plugin has a single plugins/hooks/tests.js rather than the tests/ directory the test on master plugs into.

What

An app document carries the credentials that authenticate writes to that app: key (the sdk key), keys[] (every rotated key), id_key, salt and checksum_salt. Four internal events carry such a document into the hooks pipeline:

dispatch	payload
plugins/crashes/api/api.js /crashes/new	{crash, user, app}
api/parts/mgmt/apps.js /i/apps/update	{app: appBefore, update}
api/parts/mgmt/apps.js /i/apps/reset	the app document
api/parts/mgmt/apps.js /i/apps/delete	the app document

Hooks hands the payload to its effects, and an effect can emit it verbatim: the http effect's body is a template, and {{payload_json}} stringifies the whole payload to a url the hook's author chose. So a member who can create a hook on an app could have those fields posted to a host they control.

Change

Remove those fields where hooks takes the payload over: the single funnel every internal event passes through in internal_event.js, before the _originalInput snapshot copies it as well.

Keyed off the event type rather than by field name, because key is an ordinary field elsewhere. An event has one, and a blanket scrub would break any hook that references it.

Why here and not at the dispatch sites

Because systemlogs records those payloads whole, deliberately, so that a deleted or reset app can be recovered afterwards. Stripping at the source would remove exactly the fields that recovery needs.

The scrub therefore works on copies and never mutates the object the other subscribers of the same dispatch see. That is safe to rely on: across the three repositories these four events have 150 subscriber registrations, and none of them reads key, keys, id_key, salt or checksum_salt.

repo	registrations	payload fields actually read
countly-server	35	appId x31, data x4, params x3
countly-enterprise-plugins	37	appId x37, data x1
countly-platform	78	appId x72, data x5, params x3

The data readers use data._id, data.update.name, data.update, data.app for a field diff, and triggerByEvent(data) in alerts. All of that survives the scrub. Checked by extracting each handler body and resolving destructuring and aliases, not by a single line grep.

Second change, correctness rather than security

Three checks compared rule.apps[0] instead of testing membership, so a hook configured with several apps only fired for the first one. The neighbouring cohort and crash checks already use indexOf. Replaced with an indexOf membership test. This one failed closed, so it never delivered across apps.

Verification

• plugins/hooks/tests/internal_event_payload.js, 16 cases, wired into plugins/hooks/tests/index.js so it actually runs: every app carrying event is stripped, the dispatched payload itself is left intact for each one, the fields an effect uses (_id, name, timezone, appId) survive, and four unrelated payloads that legitimately contain key are unchanged. Replacing the scrub with a pass through fails 5 of them.
• Lint and node --check clean on the changed files.