Add UnifiedAccountId

Author: wmontwe

feature/account/api/src/commonMain/kotlin/net/thunderbird/feature/account/UnifiedAccountId.kt

@@ -0,0 +1,31 @@
+package net.thunderbird.feature.account
+
+import kotlin.uuid.ExperimentalUuidApi
+import kotlin.uuid.Uuid
+import net.thunderbird.core.architecture.model.Id
+
+/**
+ * Constant for the unified account ID.
+ *
+ * This ID is used to identify the unified account, which is a special account for aggregation purposes.
+ *
+ * The unified account ID is represented by a nil UUID (all zeros).
+ *
+ * See [RFC 4122 Section 4.1.7](https://datatracker.ietf.org/doc/html/rfc4122#section-4.1.7) for more details on nil UUIDs.
+ */
+@OptIn(ExperimentalUuidApi::class)
+val UnifiedAccountId: AccountId = Id(Uuid.NIL)
+
+/**
+ * Extension property to check if an [AccountId] is the unified account ID.
+ */
+val AccountId.isUnified: Boolean
+    get() = this == UnifiedAccountId
+
+/**
+ * Ensures that the [AccountId] is not the unified account ID.
+ */
+fun AccountId.requireReal(): AccountId {
+    check(!isUnified) { "Operation not allowed on unified account" }
+    return this
+}

feature/account/api/src/commonTest/kotlin/net/thunderbird/feature/account/UnifiedAccountIdTest.kt

@@ -0,0 +1,41 @@
+package net.thunderbird.feature.account
+
+import assertk.assertFailure
+import assertk.assertThat
+import assertk.assertions.hasMessage
+import assertk.assertions.isEqualTo
+import assertk.assertions.isFalse
+import assertk.assertions.isTrue
+import kotlin.test.Test
+
+class UnifiedAccountIdTest {
+
+    @Test
+    fun `unified account id is nil uuid`() {
+        assertThat(UnifiedAccountId.asRaw()).isEqualTo("00000000-0000-0000-0000-000000000000")
+    }
+
+    @Test
+    fun `isUnified returns true for unified account id`() {
+        assertThat(UnifiedAccountId.isUnified).isTrue()
+    }
+
+    @Test
+    fun `isUnified returns false for non-unified account id`() {
+        val nonUnifiedAccountId = AccountIdFactory.of("123e4567-e89b-12d3-a456-426614174000")
+        assertThat(nonUnifiedAccountId.isUnified).isFalse()
+    }
+
+    @Test
+    fun `requireReal returns the same id if not unified`() {
+        val nonUnifiedAccountId = AccountIdFactory.of("123e4567-e89b-12d3-a456-426614174000")
+        assertThat(nonUnifiedAccountId.requireReal()).isEqualTo(nonUnifiedAccountId)
+    }
+
+    @Test
+    fun `requireReal throws exception if unified`() {
+        assertFailure {
+            UnifiedAccountId.requireReal()
+        }.hasMessage("Operation not allowed on unified account")
+    }
+}