Fix newconferencegroup api only adding the last user

Author: rubengees

library/src/main/kotlin/me/proxer/library/api/messenger/InternalApi.kt

@@ -44,7 +44,7 @@ internal interface InternalApi {
     fun createConferenceGroup(
         @Field("topic") topic: String?,
         @Field("text") firstMessage: String?,
-        @Field("users") participants: List<String>?
+        @Field("users[]") participants: List<String>?
     ): ProxerCall<String>
 
     @FormUrlEncoded

library/src/test/kotlin/me/proxer/library/api/messenger/CreateConferenceGroupEndpointTest.kt

@@ -45,6 +45,8 @@ class CreateConferenceGroupEndpointTest : ProxerTest() {
                 .execute()
         }
 
-        request.body.readUtf8() shouldEqual "topic=topic&text=message&users=someUser&users=anotherUser&users=testUser"
+        request.body.readUtf8() shouldEqual """
+            topic=topic&text=message&users%5B%5D=someUser&users%5B%5D=anotherUser&users%5B%5D=testUser
+        """.trimIndent().replace("\n", "")
     }
 }

library/src/test/kotlin/me/proxer/library/internal/interceptor/HeaderInterceptorTest.kt

@@ -35,7 +35,7 @@ class HeaderInterceptorTest : ProxerTest() {
             api.notifications.news().build().execute()
         }
 
-        request.headers.get("proxer-api-key") shouldEqual "mock-key"
+        request.headers["proxer-api-key"] shouldEqual "mock-key"
     }
 
     @Test
@@ -44,7 +44,7 @@ class HeaderInterceptorTest : ProxerTest() {
             api.notifications.news().build().execute()
         }
 
-        request.headers.get("User-Agent") shouldEqual "ProxerLibJava/$VERSION"
+        request.headers["User-Agent"] shouldEqual "ProxerLibJava/$VERSION"
     }
 
     @Test