Add support for custom tip amount for publishers

[NejcZdovc]

We are getting tip amount for publisher custom banner. We need to add support for it. This needs to be reflected in site banner and panel where user can chose this amounts.

[kjozwiak]

As @NejcZdovc mentioned above, changing the tip amounts on the Publishers website isn't being reflected under the Brave client. Quick example for more context:

Here's a preview of my banner under the Publishers website (notice the custom tips):

Here's my actual website that's serving the new banner that I've created via Publishers (notice that the custom tips haven't been used):

[LaurenWags]

Verified passed with

Brave	0.59.14 Chromium: 72.0.3626.28 (Official Build) beta(64-bit)
Revision	997b1040b63bac324e815797ba52be0cd8f616ed-refs/branch-heads/3626@{#461}
OS	Mac OS X

• Verified tipping banner shows custom amounts set on publisher website:
  

Verified passed with

Brave	0.59.14 Chromium: 72.0.3626.28 (Official Build) beta(64-bit)
Revision	997b1040b63bac324e815797ba52be0cd8f616ed-refs/branch-heads/3626@{#461}
OS	Windows 7

Verified passed with

Brave	0.59.18 Chromium: 72.0.3626.28 (Official Build) beta(64-bit)
Revision	997b1040b63bac324e815797ba52be0cd8f616ed-refs/branch-heads/3626@{#461}
OS	Linux

[kjozwiak]

Attempted to tip 500 BAT to kjozwiakstaging.github.io via staging and ran into the following error:

[ RESPONSE - ReconcilePayloadCallback ]
> time: 1546891257
> result: Failure
> response: {"statusCode":503,"error":"Service Unavailable","message":"surveyor 6KTixOtZEpwfT4prbgyTG0MlPSwri6OsKsl1bSR+BuJ has 435 control surveyors, but needed 1454"}> headers cache-control: no-cache
> headers connection: keep-alive
> headers content-encoding: gzip
> headers content-type: application/json; charset=utf-8
> headers date: Mon, 07 Jan 2019 20:00:57 GMT
> headers retry-after: 5
> headers server: Cowboy
> headers transfer-encoding: chunked
> headers vary: accept-encoding
> headers via: 1.1 vegur
> headers x-rate-limit-limit: 60
> headers x-rate-limit-remaining: 59
> headers x-rate-limit-reset: 1546891317
[ END RESPONSE ]

It appears that the back-end doesn't support 500 BAT tips. Publishers team will change/remove the 500 BAT choice from the Publishers website.

Tipping 50 BAT & 100 BAT works as expected:

[ChildishGiant]

I'd love if there was a way for a user to type in how many BAT they want to send, that way the user can give as much or as little as they want. I guess some publishers wouldn't want this so maybe they could set a min & max or just disable the custom amount option. Here's a terrible 30 second mockup

[mooleshacat]

I second (or whatever number I am) this feature

[SYK-08]

I am not able to add a custom tip amount on Brave Mobile, please help.

[LaurenWags]

@SYK-08 custom tip amount will be implemented on Android with #16021