Remove refcode from P3A reports

[rillian]

Description

Per discussion today, we no longer use the refcode field of the P3A measurement associated metadata, and so we should stop reporting it.

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.38.75 Chromium: 100.0.4896.60 (Official Build) beta (64-bit)
-- | --
Revision | 6a5d10861ce8de5fce22564658033b43cb7de047-refs/branch-heads/4896@{#875}
OS | Windows 10 Version 21H2 (Build 19044.1586)

• Verifying the test plan from Remove refcode field from P3A messages brave-core#12478

Clean profile

• Confirmed messages to the p3a.brave.com endpoint list the none in the refcode field (Note: the cmd echo CesyWJC+2AQCEkADLElOLHdpbng2NC1iYywxLjM4Ljc1LGJldGEsMjIxNCwyMjE0LG5vbmUsMQAAAAAAAAAAAAAAAAAAAAAAAAAA | base64 -d needs to be executed and get the platform specific base64-coded measurement string from Contents p3a.brave.com endpoint tab in Charles)

1.37.x	1.38.x

• Confirmed message to the p3a-json.brave.com endpoint doesn't contain a refcode field in 1.38.x

1.37.x	1.38.x

Upgrade profile

Case 1: Install 1.37.x and then upgrade the profile to 1.38.x and close the browser and then set the system date to tomorrow and relaunch the browser, after relaunching the browser for ~10 mins or so, the refcode strings are removed from the http://p3a-json.brave.com/ endpoints as the refcode removal code is merged in 1.38.x

Case 2: Install 1.37.x and collect metrics with refcode and move system date to mid of next Sunday evening (i.e 10th April 12:01:00 AM which falls on Monday, on which weekly reports are collected) and then upgrade the profile to 1.38.x and collect the metrics without refcode. In Monday's report, we should be able to see both with and without refcode metrics

Case 3: Install 1.37.x and upgrade the profile to 1.38.x and close the browser, If user has not used or opened the profile for a week and if we set the clock ahead by a week and relaunch brave, the report is picking up the metrics without refcode.

[GeetaSarvadnya]

@rillian Refcode field is removed from p3a.brave.com and p3a-json.brave.com endpoints only? Browser usage pings are still showing up refcode in the response. Is that ok?

[rillian]

Yes, that's ok. The change only affects P3A.

[Uni-verse]

Verification completed on Samsung GS 21, Samsung Tab S7 using

Brave	1.38.107 Chromium: 101.0.4951.41 (Official Build) (64-bit) 
Revision	93c720db8323b3ec10d056025ab95c23a31997c9-refs/branch-heads/4951@{#904}
OS	Android 12;

Fresh Profile:

• Confirmed requests made to the p3a-json.brave.com endpoint should not contain a refcode field at all.

Upgrade Profile:

• Setting up a profile with refcode and then upgrading to 1.38 will send metrics without the refcode .
• Collect metrics with refcode, upgrade the profile and then move the clock one week ahead will send new reports without refcode.

1.37	1.38