[android] backend: APIInterface should use relative paths

for cases where baseURL contains `/api`

android/backend/src/main/java/net/buzzert/kordophone/backend/server/APIInterface.kt

@@ -55,13 +55,13 @@ data class UploadAttachmentResponse(
 )
 
 interface APIInterface {
-    @GET("/version")
+    @GET("version")
     suspend fun getVersion(): ResponseBody
 
-    @GET("/conversations")
+    @GET("conversations")
     suspend fun getConversations(): Response<List<Conversation>>
 
-    @GET("/messages")
+    @GET("messages")
     suspend fun getMessages(
         @Query("guid") conversationGUID: String,
         @Query("limit") limit: Int? = null,
@@ -69,19 +69,19 @@ interface APIInterface {
         @Query("afterMessageGUID") afterMessageGUID: GUID? = null,
     ): Response<List<Message>>
 
-    @POST("/sendMessage")
+    @POST("sendMessage")
     suspend fun sendMessage(@Body request: SendMessageRequest): Response<SendMessageResponse>
 
-    @POST("/markConversation")
+    @POST("markConversation")
     suspend fun markConversation(@Query("guid") conversationGUID: String): Response<Void>
 
-    @GET("/attachment")
+    @GET("attachment")
     suspend fun fetchAttachment(@Query("guid") guid: String, @Query("preview") preview: Boolean = false): ResponseBody
 
-    @POST("/uploadAttachment")
+    @POST("uploadAttachment")
     suspend fun uploadAttachment(@Query("filename") filename: String, @Body body: RequestBody): Response<UploadAttachmentResponse>
 
-    @POST("/authenticate")
+    @POST("authenticate")
     suspend fun authenticate(@Body request: AuthenticationRequest): Response<AuthenticationResponse>
 }
 
@@ -93,4 +93,4 @@ fun <T> Response<T>.bodyOnSuccessOrThrow(): T {
     }
 
     throw ResponseDecodeError(errorBody()!!)
-}
+}