Cashu wallet

[1-leo]

fixes #505
fixes #503
fixes #504

• fix minibits issue -> support cashu websockets (minibits) #508
• try sembast wallets/cashu repo impl in ndk core as a default db repo impl
• remove need for external mint in tests
• extract CashuRepo ops from CacheManager and adapt db impls for that -> fix: extract CashuRepo ops from CacheManager #536
• examples
• documentation
• more tests for keeping coverage high
• remove https://dev.mint.camelus.app as default mint address

[codecov]

Codecov Report

❌ Patch coverage is 64.33244% with 927 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.44%. Comparing base (5c6826f) to head (9fdfc93).
⚠️ Report is 305 commits behind head on master.

Files with missing lines	Patch %	Lines
...ndk/lib/domain_layer/usecases/wallets/wallets.dart	31.08%	184 Missing ⚠️
...ties/wallet/providers/nwc/nwc_wallet_provider.dart	3.60%	107 Missing ⚠️
...ges/ndk/lib/domain_layer/usecases/cashu/cashu.dart	81.22%	98 Missing ⚠️
.../wallet/providers/lnurl/lnurl_wallet_provider.dart	5.33%	71 Missing ⚠️
...data_layer/repositories/cashu/cashu_repo_impl.dart	73.56%	60 Missing ⚠️
.../wallet/providers/cashu/cashu_wallet_provider.dart	17.80%	60 Missing ⚠️
...lib/domain_layer/usecases/cashu/cashu_restore.dart	61.46%	42 Missing ⚠️
...main_layer/entities/wallet/wallet_transaction.dart	47.05%	36 Missing ⚠️
.../entities/wallet/providers/lnurl/lnurl_wallet.dart	0.00%	27 Missing ⚠️
...ackages/ndk/lib/domain_layer/usecases/nwc/nwc.dart	0.00%	23 Missing ⚠️
... and 33 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #194      +/-   ##
==========================================
- Coverage   76.65%   73.44%   -3.21%     
==========================================
  Files         153      195      +42     
  Lines        6407     8969    +2562     
==========================================
+ Hits         4911     6587    +1676     
- Misses       1496     2382     +886     

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[1-leo]

As a user I want to donate ecash without fees
(locked token to pubkey without swap)

[1-leo]

• Wrapper around DB operations with mutex to allow atomic operations
• Stream of pendingTransaction(base class) with extend on pendingMintTransaction where user calls .proceed() .cancel()

.