Add method to delete all private messages to REST API

Needed for https://code.briarproject.org/briar/briar-gtk/-/issues/11.

Fixes #1782

briar-headless/README.md

@@ -247,6 +247,12 @@ needs to be provided in the request body as follows:
 }
 ```
 
+### Deleting all private messages
+
+`DELETE /v1/messages/{contactId}/all`
+
+It returns with a status code `200`, if removal was successful.
+
 ### Listing blog posts
 
 `GET /v1/blogs/posts`

briar-headless/src/main/java/org/briarproject/briar/headless/Router.kt

@@ -89,6 +89,9 @@ constructor(
                 path("/messages/:contactId/read") {
                     post { ctx -> messagingController.markMessageRead(ctx) }
                 }
+                path("/messages/:contactId/all") {
+                    delete { ctx -> messagingController.deleteAllMessages(ctx) }
+                }
                 path("/forums") {
                     get { ctx -> forumController.list(ctx) }
                     post { ctx -> forumController.create(ctx) }

briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingController.kt

@@ -10,4 +10,6 @@ interface MessagingController {
 
     fun markMessageRead(ctx: Context): Context
 
+    fun deleteAllMessages(ctx: Context): Context
+
 }

briar-headless/src/main/java/org/briarproject/briar/headless/messaging/MessagingControllerImpl.kt

@@ -106,6 +106,16 @@ constructor(
         return MessageId(idBytes)
     }
 
+    override fun deleteAllMessages(ctx: Context): Context {
+        val contactId = ctx.getContactIdFromPathParam()
+        try {
+            conversationManager.deleteAllMessages(contactId)
+        } catch (e: NoSuchContactException) {
+            throw NotFoundResponse()
+        }
+        return ctx
+    }
+
     override fun eventOccurred(e: Event) {
         when (e) {
             is ConversationMessageReceivedEvent<*> -> {

briar-headless/src/test/java/org/briarproject/briar/headless/messaging/MessagingControllerImplTest.kt

@@ -17,6 +17,7 @@ import org.briarproject.bramble.test.ImmediateExecutor
 import org.briarproject.bramble.test.TestUtils.getRandomId
 import org.briarproject.bramble.util.StringUtils.getRandomString
 import org.briarproject.briar.api.client.SessionId
+import org.briarproject.briar.api.conversation.DeletionResult
 import org.briarproject.briar.api.introduction.IntroductionRequest
 import org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_TEXT_LENGTH
 import org.briarproject.briar.api.messaging.MessagingManager
@@ -343,6 +344,30 @@ internal class MessagingControllerImplTest : ControllerTest() {
         assertJsonEquals(json, request.output(contact.id))
     }
 
+    @Test
+    fun testDeleteAllMessages() {
+        every { ctx.pathParam("contactId") } returns "1"
+        every { conversationManager.deleteAllMessages(ContactId(1)) } returns DeletionResult()
+        controller.deleteAllMessages(ctx)
+    }
+
+    @Test
+    fun testDeleteAllMessagesInvalidContactId() {
+        every { ctx.pathParam("contactId") } returns "foo"
+        assertThrows(NotFoundResponse::class.java) {
+            controller.deleteAllMessages(ctx)
+        }
+    }
+
+    @Test
+    fun testDeleteAllMessagesNonexistentContactId() {
+        every { ctx.pathParam("contactId") } returns "1"
+        every { conversationManager.deleteAllMessages(ContactId(1)) } throws NoSuchContactException()
+        assertThrows(NotFoundResponse::class.java) {
+            controller.deleteAllMessages(ctx)
+        }
+    }
+
     private fun expectGetContact() {
         every { ctx.pathParam("contactId") } returns contact.id.int.toString()
         every { contactManager.getContact(contact.id) } returns contact