Fix production credit service wiring

Register the credits service through its route-facing interface and verify the application module resolves the binding without touching MySQL.

src/test/kotlin/com/osglab/account/ApplicationTest.kt

@@ -1,10 +1,19 @@
 package com.osglab.account
 
+import com.osglab.account.config.AppConfig
+import com.osglab.account.features.credits.repositories.BillingTransactionRunner
+import com.osglab.account.features.credits.repositories.BillingUnitOfWork
+import com.osglab.account.features.credits.services.CreditOperations
+import com.osglab.account.features.credits.services.CreditService
 import io.kotest.matchers.shouldBe
 import io.ktor.client.request.get
 import io.ktor.http.HttpStatusCode
+import io.ktor.server.config.MapApplicationConfig
 import io.ktor.server.routing.routing
 import io.ktor.server.testing.testApplication
+import org.koin.dsl.koinApplication
+import org.koin.dsl.module
+import java.util.Base64
 import kotlin.test.Test
 
 class ApplicationTest {
@@ -16,4 +25,49 @@ class ApplicationTest {
 
         client.get("/health/live").status shouldBe HttpStatusCode.OK
     }
+
+    @Test
+    fun `application module exposes credit operations through its interface`() {
+        val transactionRunner = object : BillingTransactionRunner {
+            override suspend fun <T> inTransaction(block: (BillingUnitOfWork) -> T): T =
+                error("Transaction runner is not used while resolving dependencies")
+        }
+        val application = koinApplication {
+            allowOverride(true)
+            modules(accountServerModule(testModuleConfig()))
+            modules(module { single<BillingTransactionRunner> { transactionRunner } })
+        }
+
+        try {
+            application.koin.get<CreditOperations>() shouldBe
+                application.koin.get<CreditService>()
+        } finally {
+            application.close()
+        }
+    }
 }
+
+private fun testModuleConfig(): AppConfig = AppConfig.from(
+    MapApplicationConfig(
+        "app.environment" to "test",
+        "app.database.jdbcUrl" to "jdbc:mysql://localhost:3306/test",
+        "app.database.username" to "test",
+        "app.database.password" to "database-password",
+        "app.database.migrationUsername" to "test_migrator",
+        "app.database.migrationPassword" to "migration-password",
+        "app.database.maximumPoolSize" to "4",
+        "app.session.issuer" to "https://issuer.example",
+        "app.session.audience" to "ios-app",
+        "app.session.secret" to "01234567890123456789012345678901",
+        "app.session.accessMinutes" to "15",
+        "app.session.refreshDays" to "30",
+        "app.encryption.keyBase64" to Base64.getEncoder().encodeToString(ByteArray(32) { 7 }),
+        "app.antiAbuse.identityHmacKeyBase64" to Base64.getEncoder().encodeToString(ByteArray(32) { 8 }),
+        "app.apple.clientId" to "com.example.app",
+        "app.apple.jwksUrl" to "https://appleid.apple.com/auth/keys",
+        "app.apple.tokenUrl" to "https://appleid.apple.com/auth/token",
+        "app.apple.revokeUrl" to "https://appleid.apple.com/auth/revoke",
+        "app.integrity.enforceDeviceCheck" to "false",
+        "app.integrity.enforceAppAttest" to "false",
+    ),
+)