Add Dangerbot rule to check additional properties being passed twice

The following discussion from !208043 (merged) should be addressed:

• @nbelokolodov started a discussion:

  I see usability problem here, will create a follow up issue to address situations when developers mix old and new syntax to avoid confusion

Problem

With the new syntax where additional_properties are extracted from args its possible to developers to pass properties in the both parameters, for example

track_event('event',
  user: user,
  label: label, # new syntax
  additional_properties: {
    name: name # old syntax
  }
)

in this situation label will be lost since additional_properties is provided

Desired Outcome

Design and implement a foolproof solution for both tracking code syntaxes (old and new syntax) to coexists for some time before the old code will be migrated (potentially years)

Potential Solution

Solution 1:

We could merge explicit and implicit additional properties silently to avoid any tracking data loss. It solve the problem with developers using wrong syntax but the tracking code will be incorrect and potentially confusing.

Solution 2

Add Dangerbot rule to verify additional_properties are not used with new syntax

Documentation Update Needed

• Yes
• No

How to verify

Further actions needed