Pending transfers endpoint misses payment amount

[manuelwedler]

Problem Definition

The pending_transfers endpoint should give the actual payment amount. At the moment it only returns the locked_amount. If you do the same payment twice the locked amount is increased. See for example this response of the pending_transfers endpoint after doing two payments of 100 tokens:

[{"payment_identifier": "1575988839973", "token_address": "0x31aA9D3E2bd38d22CA3Ae9be7aae1D518fe46043", "token_network_address": "0x4FFe30a4342c1089fEd71392356F9403723E925c", "channel_identifier": "40", "initiator": "0x65A148DE5d57279EB9FdFe8c11cF9A43E599a537", "target": "0x7deA0108AB75a8CF373c02bdb237664A31fcf48B", "transferred_amount": "4063362541100001017", "locked_amount": "100", "role": "initiator"}, 
{"payment_identifier": "1575988841305", "token_address": "0x31aA9D3E2bd38d22CA3Ae9be7aae1D518fe46043", "token_network_address": "0x4FFe30a4342c1089fEd71392356F9403723E925c", "channel_identifier": "40", "initiator": "0x65A148DE5d57279EB9FdFe8c11cF9A43E599a537", "target": "0x7deA0108AB75a8CF373c02bdb237664A31fcf48B", "transferred_amount": "4063362541100001017", "locked_amount": "200", "role": "initiator"}]

So the second payment does not show the actual payment amount. After the first payment is completed the locked amount of the second pending transfer stays the same, which makes it not possible to calculate the actual payment amount anymore.

I would like to see an additional field amount on every pending transfer that shows the actual value.

System Description

Raiden v0.200.0-rc2