Use new Uphold sandbox URL

[zenparsing]

The new URL should look like https://wallet-sandbox.uphold.com/...

The original message from Uphold:

You are being reached out to as you are an API partner of Uphold and have an authorized Sandbox account.
This is a friendly notification that if you are testing in the Uphold Sandbox, please make sure to use the new sandbox URL from
now on: http://wallet-sandbox.uphold.com/. In particular, this means that the OAuth authorization URL should be changed
from https://sandbox.uphold.com/ to https://wallet-sandbox.uphold.com/.

Note: Per Uphold, this does not affect the REST API endpoint (api-sandbox.uphold.com).

[emerick]

I switched over to use the new sandbox URL in a local build, but the "Withdraw Funds" link takes me to a blank page. Uphold is aware of this issue and is working on a fix as of 4/8/21.

[stephendonner]

Verified PASSED using

Brave	1.25.19 Chromium: 90.0.4430.72 (Official Build) nightly (x86_64)
Revision	b6172ef8d07ef486489a4b11b66b2eaeed50d132-refs/branch-heads/4430@{#1233}
OS	macOS Version 11.2.3 (Build 20D91)

Steps:

1. new profile
2. launched Brave using --enable-logging=stderr --vmodule="*/bat-native-ledger/*"=6,"*/brave_rewards/*"=6,"*/bat-native-ads/*"=6,"*/bat-native-confirmations/*"=6,"*/brave_ads/*"=9,"*/brave_user_model/*"=6 --brave-ads-staging --brave-ads-debug --rewards=staging=true,reconcile-interval=4
3. claimed UGP BAT grant
4. verified Uphold wallet and confirmed that this uses the correct URL (https://wallet-sandbox.uphold.com/...)
5. verified clicking on Add funds took me to the correct page with the Brave card in the "To" field
6. verified clicking on Withdraw funds took me to the correct page with the Brave card in the "From" field
7. verified that visiting the Uphold dashboard worked as expected

example	example	example	example	example	example	example	example	example

---

Verification passed on

Brave	1.25.59 Chromium: 90.0.4430.212 (Official Build) beta (64-bit)
Revision	e3cd97fc771b893b7fd1879196d1215b622c2bed-refs/branch-heads/4430@{#1429}
OS	Ubuntu 18.04 LTS

Verified test plan from brave/brave-core#8492

---

Verification passed on

Brave | 1.25.57 Chromium: 90.0.4430.93 (Official Build) beta (64-bit)
-- | --
Revision | 4df112c29cfe9a2c69b14195c0275faed4e997a7-refs/branch-heads/4430@{#1348}
OS | Windows 10 OS Version 2004 (Build 19041.985)

Verified test plan from brave/brave-core#8492

• Confirmed one time tips can be set to verified pubs using uphold wallet
• Confirmed transaction amount is shown correctly
• Confirmed Uphold dashboard works as expected

example	example	example	example	example	example	example

logs for 95% contribution

[ REQUEST ]
> URL: https://api-sandbox.uphold.com/v0/me/cards/....../transactions
> Method: UrlMethod::POST
> Content: {"denomination":{"amount":"4.750000","currency":"BAT"},"destination":"abf1ff79-a239-42af-abff-20eb121edd1c","message":""}
> Content Type: application/json; charset=utf-8
[8284:17316:0513/174713.875:VERBOSE6:logging_util.cc(136)]
[ RESPONSE - OnRequest ]
> Url: https://api-sandbox.uphold.com/v0/me/cards/......../transactions
> Result: Success
> HTTP Code: 202
> Body: {"createdAt":"2021-05-13T12:17:13.675Z","denomination":{"amount":"4.75","

logs for 5% contribution

[ REQUEST ]
> URL: https://api-sandbox.uphold.com/v0/me/cards/......./transactions
> Method: UrlMethod::POST
> Content: {"denomination":{"amount":"0.250000","currency":"BAT"},"destination":"1b2b466f-5c15-49bf-995e-c91777d3da93","message":"5% transaction fee collected by Brave Software International"}
> Content Type: application/json; charset=utf-8
[8284:17316:0513/174726.349:VERBOSE6:logging_util.cc(136)]
[ RESPONSE - OnRequest ]
> Url: https://api-sandbox.uphold.com/v0/me/cards/......../transactions
> Result: Success
> HTTP Code: 202
> Body: {"createdAt":"2021-05-13T12:17:26.122Z","denomination":{"amount":"0.25",