prepare payment intent flow, add failing test: payment metadata handling is broken
refactor payment test: single test
add failing test for #99
schema: add index for payment metadata timestamp
add payment metadata selectio  (explicit)
payment metadata db, select metadata on payment web handler
Merge pull request #100 from wongak/99-payment_metadata

99 payment metadata
describe debug intent worker, first bulding block for #88
paymentd: add debugging capabilities: sig USR1 will panic for trace
describe IntentWorker architecture
add IntentPaid, refactor intent handling
Merge pull request #101 from wongak/88-payment_flow

First pass of payment service handling intents finished
rework payment flow: separate intent workers, implement changes

See #88
fix test
include payment metadata in notification
fix not passing ranged var to goroutine
docs for intent workers
Merge pull request #102 from wongak/payment_handling

Payment handling