Add claim date to promotion

[NejcZdovc]

Right now we don't track when user claimed a promotion. We need this info for monthly statement, so we should start logging it in DB.

[GeetaSarvadnya]

Verification passed on

Brave	1.4.84 Chromium: 80.0.3987.87 (Official Build) beta (64-bit)
Revision	449cb163497b70dbf98d389f54e38e85d4c59b43-refs/branch-heads/3987@{#801}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified that claimed_at parameter is NOT available in 1.3.x and previous versions
• Verified that claimed_at parameter is added in the promotion table in 1.4.x
• Verified that claimed_at parameter is showing timestamp value as 0 before claiming UGP grants
• Verified that claimed_at parameter is showing grants claimed timestamp after claiming UGP grants

Before claiming UGP grants:

After claiming UGP grants:

• Verified in clean and upgraded profile (claim UGP grants in 1.3.x and upgrade to 1.4.x shows the claimed_at value as 0 which is as expected as the UGP grant is claimed in 1.3.x )
• Logged claimed_at db timestamp value resets to zero after sending one time or recurring tip #8180

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Verification passed on

Brave	1.4.86 Chromium: 80.0.3987.87 (Official Build) beta (64-bit)
Revision	449cb163497b70dbf98d389f54e38e85d4c59b43-refs/branch-heads/3987@{#801}
OS	Ubuntu 18.04 LTS

• Verified that claimed_at parameter is NOT available in 1.3.x and previous versions
• Verified that claimed_at parameter is added in the promotion table in 1.4.x
• Verified that claimed_at parameter is showing timestamp value as 0 before claiming UGP grants
• Verified that claimed_at parameter is showing grants claimed timestamp after claiming UGP grants

Before claiming UGP grants:

After claiming UGP grants:

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Verification PASSED on macOS 10.15.3 x64 using the following build:

Brave	1.4.93 Chromium: 80.0.3987.116 (Official Build) (64-bit)
Revision	dc00a510e4c2ae25c4d084cc3d946fc782249224-refs/branch-heads/3987@{#917}
OS	macOS Version 10.15.3 (Build 19D76)

• ensured that claimed_at wasn't available under the promotion table on 1.3.118 CR: 80.0.3987.116
  • claimed a ugp & ad grant and ensured that it appeared in the promotion table without claimed_at
• ensured that claimed_at is visible/being used under the promotion table on 1.4.93 CR: 80.0.3987.116
  • ensured that both ugp & ad grants have a value of 0 under claimed_at (not claimed)
  • ensured that the timestamp appears under claimed_at when claiming both ugp & ad grants

Before claiming both UGP & Ad Grants:

After claiming both UGP & Ad Grants:

• ensured that you can claim one of the available grants under 1.3.118 CR: 80.0.3987.116 and upgrade to 1.4.93 CR: 80.0.3987.116 to claim the second available grant
  • ensured that claimed_at appears as Null for 1.3.118 CR: 80.0.3987.116
  • ensured that claimed_at displays the correct timestamp under 1.4.93 CR: 80.0.3987.116

Example: