fix: satisfy card creation validation payload requirements

Send required create-card fields and retry with alias keys when canonical payload is rejected, so board add-card works across stricter Kan API variants.

app/src/main/java/space/hackenslacker/kanbn4droid/app/auth/KanbnApiClient.kt

@@ -387,25 +387,47 @@ class HttpKanbnApiClient : KanbnApiClient {
         tagPublicIds: List<String>,
     ): BoardsApiResult<CreatedEntityRef> {
         return withContext(Dispatchers.IO) {
-            val payloadFields = mutableListOf(
+            val canonicalPayload = buildCreateCardPayload(
-                "\"listPublicId\":\"${jsonEscape(listPublicId)}\"",
+                listPublicId = listPublicId,
-                "\"title\":\"${jsonEscape(title)}\"",
+                title = title,
-                "\"index\":0",
+                description = description,
-                "\"labelPublicIds\":${jsonStringArray(tagPublicIds)}",
+                dueDate = dueDate,
+                tagPublicIds = tagPublicIds,
+                aliasKeys = false,
             )
-            if (description != null) {
+            val canonicalResult = request(
-                payloadFields += "\"description\":\"${jsonEscape(description)}\""
+                baseUrl = baseUrl,
+                path = "/api/v1/cards",
+                method = "POST",
+                apiKey = apiKey,
+                body = canonicalPayload,
+            ) { code, body ->
+                if (code in 200..299) {
+                    parseCreatedEntityRef(body)
+                        ?.let { BoardsApiResult.Success(it) }
+                        ?: BoardsApiResult.Failure("Malformed create card response.")
+                } else {
+                    BoardsApiResult.Failure(serverMessage(body, code))
+                }
             }
-            if (dueDate != null) {
+            if (canonicalResult is BoardsApiResult.Success) {
-                payloadFields += "\"dueDate\":\"${dueDate}T00:00:00Z\""
+                return@withContext canonicalResult
             }
-            val payload = "{${payloadFields.joinToString(",")}}"
+
+            val aliasPayload = buildCreateCardPayload(
+                listPublicId = listPublicId,
+                title = title,
+                description = description,
+                dueDate = dueDate,
+                tagPublicIds = tagPublicIds,
+                aliasKeys = true,
+            )
             request(
                 baseUrl = baseUrl,
                 path = "/api/v1/cards",
                 method = "POST",
                 apiKey = apiKey,
-                body = payload,
+                body = aliasPayload,
             ) { code, body ->
                 if (code in 200..299) {
                     parseCreatedEntityRef(body)
@@ -418,6 +440,44 @@ class HttpKanbnApiClient : KanbnApiClient {
         }
     }
 
+    private fun buildCreateCardPayload(
+        listPublicId: String,
+        title: String,
+        description: String?,
+        dueDate: LocalDate?,
+        tagPublicIds: List<String>,
+        aliasKeys: Boolean,
+    ): String {
+        val payloadFields = mutableListOf(
+            "\"listPublicId\":\"${jsonEscape(listPublicId)}\"",
+            if (aliasKeys) {
+                "\"name\":\"${jsonEscape(title)}\""
+            } else {
+                "\"title\":\"${jsonEscape(title)}\""
+            },
+            "\"description\":\"${jsonEscape(description.orEmpty())}\"",
+            "\"labelPublicIds\":${jsonStringArray(tagPublicIds)}",
+            "\"memberPublicIds\":[]",
+            "\"position\":\"start\"",
+        )
+        if (aliasKeys) {
+            payloadFields += if (aliasKeys) {
+                "\"body\":\"${jsonEscape(description.orEmpty())}\""
+            } else {
+                "\"description\":\"${jsonEscape(description.orEmpty())}\""
+            }
+            payloadFields += "\"index\":0"
+        }
+        if (dueDate != null) {
+            payloadFields += if (aliasKeys) {
+                "\"dueAt\":\"${dueDate}T00:00:00Z\""
+            } else {
+                "\"dueDate\":\"${dueDate}T00:00:00Z\""
+            }
+        }
+        return "{${payloadFields.joinToString(",")}}"
+    }
+
     override suspend fun moveCard(
         baseUrl: String,
         apiKey: String,

app/src/test/java/space/hackenslacker/kanbn4droid/app/auth/HttpKanbnApiClientBoardDetailParsingTest.kt

@@ -99,7 +99,7 @@ class HttpKanbnApiClientBoardDetailParsingTest {
     }
 
     @Test
-    fun createCard_sendsTopIndex_andOmittedDueDateWhenNull() = runTest {
+    fun createCard_sendsRequiredValidationFields_whenOptionalsAreNull() = runTest {
         TestServer().use { server ->
             server.register(path = "/api/v1/cards", method = "POST", status = 200, responseBody = """{"publicId":"card-new"}""")
 
@@ -116,9 +116,10 @@ class HttpKanbnApiClientBoardDetailParsingTest {
             assertTrue(result is BoardsApiResult.Success<*>)
             val request = server.findRequest("POST", "/api/v1/cards")
             assertNotNull(request)
-            assertTrue(request?.body?.contains("\"index\":0") == true)
+            assertTrue(request?.body?.contains("\"position\":\"start\"") == true)
+            assertTrue(request?.body?.contains("\"memberPublicIds\":[]") == true)
+            assertTrue(request?.body?.contains("\"description\":\"\"") == true)
             assertTrue(request?.body?.contains("\"dueDate\"") == false)
-            assertTrue(request?.body?.contains("\"description\"") == false)
         }
     }
 
@@ -172,6 +173,36 @@ class HttpKanbnApiClientBoardDetailParsingTest {
         }
     }
 
+    @Test
+    fun createCard_retriesWithAliasPayloadWhenServerRejectsCanonicalFields() = runTest {
+        TestServer().use { server ->
+            server.registerSequence(
+                path = "/api/v1/cards",
+                method = "POST",
+                responses = listOf(
+                    400 to "{}",
+                    200 to """{"card":{"publicId":"card-new"}}""",
+                ),
+            )
+
+            val result = HttpKanbnApiClient().createCard(
+                baseUrl = server.baseUrl,
+                apiKey = "api",
+                listPublicId = "list-1",
+                title = "Card",
+                description = "Description",
+                dueDate = LocalDate.of(2026, 3, 16),
+                tagPublicIds = listOf("tag-1"),
+            )
+
+            assertTrue(result is BoardsApiResult.Success<*>)
+            val requests = server.findRequests("POST", "/api/v1/cards")
+            assertEquals(2, requests.size)
+            assertTrue(requests[0].body.contains("\"title\":\"Card\""))
+            assertTrue(requests[1].body.contains("\"name\":\"Card\""))
+        }
+    }
+
     @Test
     fun getBoardDetailParsesWrappedPayloadWithDueDateVariants() = runTest {
         TestServer().use { server ->