feat: add SNIP-29 Paymaster SDK for gasless transactions and flexible gas payments

packages/starknet_paymaster/CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.0] - 2024-01-XX
+
+### Added
+- Initial release of SNIP-29 compliant Paymaster SDK for Dart
+- Full implementation of SNIP-29 Paymaster API specification
+- Support for gasless (sponsored) transactions
+- Support for ERC-20 token fee payments
+- Comprehensive type-safe API with proper error handling
+- Transaction tracking and status monitoring
+- Integration with AVNU Paymaster service
+- Complete test coverage including unit, integration, and E2E tests
+- Comprehensive documentation and examples
+- Validation utilities for all paymaster data types
+- JSON-RPC client with automatic error handling
+- Support for time-bounded transactions
+- Backwards compatibility with existing starknet.dart applications
+
+### Features
+- `PaymasterClient` - Main client for SNIP-29 API interactions
+- `PaymasterConfig` - Configuration management with AVNU presets
+- `PaymasterTransaction` - Type-safe transaction models
+- `PaymasterExecution` - Execution parameter management
+- Complete error handling with specific exception types
+- Automatic transaction tracking and polling
+- Fee estimation capabilities
+- Support for deploy, invoke, and deploy+invoke transactions
+- Signature utilities and validation
+- Network resilience and timeout handling
+
+### API Methods
+- `isAvailable()` - Check paymaster service status
+- `getSupportedTokensAndPrices()` - Get supported tokens and pricing
+- `buildTypedData()` - Build typed data for signing
+- `execute()` - Execute signed transactions
+- `executeTransaction()` - Complete transaction flow
+- `executeSponsoredTransaction()` - Gasless transaction execution
+- `executeErc20Transaction()` - ERC-20 fee payment execution
+- `trackingIdToLatestHash()` - Transaction status tracking
+- `waitForTransaction()` - Wait for transaction completion
+- `getFeeEstimate()` - Get transaction fee estimates

packages/starknet_paymaster/LICENSE

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+MIT License
+
+Copyright (c) 2024 AVNU Labs
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.