WIP: New melt flow (#622)

* `PaymentResult`

* ledger: rely on PaymentResult instead of paid flag. Double check for payments marked pending.

* `None` is `PENDING`

* make format

* reflected changes API tests where `PaymentStatus` is used + reflected changes in lnbits

* reflect changes in blink backend and tests

* fix lnbits get_payment_status

* remove paid flag

* fix mypy

* remove more paid flags

* fix strike mypy

* green

* shorten all state checks

* fix

* fix some tests

* gimme ✅

* fix............

* fix lnbits

* fix error

* lightning refactor

* add more regtest tests

* add tests for pending state and failure

* shorten checks

* use match case for startup check - and remember modified checking_id from pay_invoice

* fix strike pending return

* new tests?

* refactor startup routine into get_melt_quote

* test with purge

* refactor blink

* cleanup responses

* blink: return checking_id on failure

* fix lndgrpc try except

* add more testing for melt branches

* speed things up a bit

* remove comments

* remove comments

* block pending melt quotes

* remove comments

---------

Co-authored-by: lollerfirst <lollerfirst@gmail.com>

tests/conftest.py

@@ -48,7 +48,7 @@ settings.mint_seed_decryption_key = ""
 settings.mint_max_balance = 0
 settings.mint_transaction_rate_limit_per_minute = 60
 settings.mint_lnd_enable_mpp = True
-settings.mint_clnrest_enable_mpp = False
+settings.mint_clnrest_enable_mpp = True
 settings.mint_input_fee_ppk = 0
 settings.db_connection_pool = True