Migrate surf-transaction to Microservice Architecture with RabbitMQ

[Copilot]

Migrates surf-transaction from a monolithic core module (direct DB access on Paper/Velocity) to a proper microservice architecture where client plugins communicate with a standalone microservice via RabbitMQ.

Module restructure

Module	Before	After
surf-transaction-core	All implementation	Pure Gradle container (no src/)
surf-transaction-core-common	—	NEW Shared DTOs, Core*Service interfaces, Redis, RabbitMQ packets
surf-transaction-core-client	—	NEW RabbitMQ-backed service impls (@AutoService)
surf-transaction-microservice	—	NEW Standalone microservice: DB, handlers, entry point
surf-transaction-paper/velocity	Depends on :core	Depends on :core:core-client, CLIENT_API RabbitMQ

Core interfaces

Introduced CoreAccountService, CoreCurrencyService, CoreTransactionService extending the API interfaces with the extra methods (e.g. getDefaultAccount, deleteAccount, addMemberToAccount). TransactionalImpl, AccountAccessImpl, and AccountMemberOperationsImpl now resolve to these via service locator — transparently dispatching to either DB-backed or RabbitMQ-backed impls depending on the JVM.

RabbitMQ packets (core-common)

16 @Serializable Request/Response pairs covering all service operations. TransactionResultPacket is a new sealed class for safe wire transport of TransactionResult subtypes.

@Serializable
class DepositRequest(
    val accountId: SerializableStringUUID,
    val initiator: SerializableStringUUID,
    val amount: SerializableBigDecimal,
    val currencyName: String,
    val ignoreMinimum: Boolean,
    val additionalData: Set<TransactionData>
) : RabbitRequestPacket<DepositResponse>()

Microservice entry point & handler

TransactionMicroservice bootstraps the instance and registers TransactionRabbitHandler. All @RabbitHandler methods use request.launch {} (no runBlocking) since RabbitRequestPacket implements CoroutineScope.

@RabbitHandler
fun handleDeposit(request: DepositRequest) {
    request.launch {
        val result = CoreTransactionService.get().deposit(...)
        request.respond(DepositResponse(result.toPacket()))
    }
}

Serialization additions

• @Serializable added to: AccountDeleteResult, AccountMemberResult, AccountCreationResult.FailureReason, CurrencyCreateResult, CurrencyDefaultResult, TransactionImpl
• Binary compatibility file updated to reflect new serializer() companion methods on affected enums

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