Support Create Multireddit api method

Author: mrboisvert

src/main/java/org/quantumbadger/redreader/common/Constants.java

@@ -149,6 +149,8 @@ public static final class Reddit {
 		public static final String PATH_MULTIREDDITS_MINE = "/api/multi/mine.json";
 		public static final String PATH_COMMENTS = "/comments/";
 		public static final String PATH_ME = "/api/v1/me";
+		public static final String PATH_MULTIREDDIT = "/api/multi";
+
 
 		public static String getScheme() {
 			return SCHEME_HTTPS;

src/main/java/org/quantumbadger/redreader/reddit/RedditAPI.java

@@ -25,6 +25,8 @@
 import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
 
+import org.json.JSONArray;
+import org.json.JSONObject;
 import org.quantumbadger.redreader.account.RedditAccount;
 import org.quantumbadger.redreader.activities.BugReportActivity;
 import org.quantumbadger.redreader.cache.CacheManager;
@@ -65,6 +67,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -959,6 +962,35 @@ public void onFailure(@NonNull final RRError error) {
 		));
 	}
 
+	public static void createMultireddit(
+		final CacheManager cm,
+		final APIResponseHandler.ActionResponseHandler handler,
+		final RedditAccount user,
+		final String multiredditName,
+		final List<String> subredditNames,
+		final Context context) {
+
+		final Uri.Builder builder = Constants.Reddit.getUriBuilder(
+				Constants.Reddit.PATH_MULTIREDDIT)
+			.appendPath("user")
+			.appendPath(user.username)
+			.appendPath("m")
+			.appendPath(multiredditName);
+
+		final Map<String, String> jsonData = new HashMap<>();
+		jsonData.put("display_name", multiredditName);
+		jsonData.put("visibility", "private");
+		jsonData.put("subreddits", new JSONArray(subredditNames).toString());
+
+		cm.makeRequest(createPostRequest(
+			UriString.from(builder.build()),
+			user,
+			new ArrayList<>(Collections.singleton(
+				new PostField("model", new JSONObject(jsonData).toString()))),
+			context,
+			new GenericResponseHandler(handler)));
+	}
+
 	@Nullable
 	private static APIResponseHandler.APIFailureType findFailureType(final JsonValue response) {