Allow rules to specify the base part of their response keys

[csams]

When a rule returns make_fail(ERROR_KEY, ...), the key generated is actually the rule's module name combined with ERROR_KEY. This means renaming a rule's module affects its responses, which can break hit history in downstream systems.

We need something like @rule(..., identity="foo_bar"baz") to cause the module name portion of the rule's response keys to always be "foo_bar_baz" instead of whatever the module name happens to be. Then developers will be free to reorganize existing rules.

[koalakangaroo]

This is a valid point to me to keep the rule hit history (trend) consistent before and after the ERROR KEY is renamed.

[sbunciak]

just a quick question @csams - is this going to affect existing reporting in some way? is this identity attribute going to translate to rule_ids we see today in datahub?

[csams]

@sbunciak Today a rule_id is made by convention from the rule's base module name and a response key.

The enhancement would let developers explicitly set the module part of the id so they can move rules around and rename modules without breaking content lookup and report history.

[sbunciak]

@csams could we also add a version property? I'm thinking we could then use it to version rules and once Advisor detects a new version of a rule we could emit an 'updated recommendation' event type in Notifications service. cc @dkuc