implement announcements

closes #127

mastodon/src/main/java/org/joinmastodon/android/model/Announcement.java

@@ -0,0 +1,63 @@
+package org.joinmastodon.android.model;
+
+import org.joinmastodon.android.api.RequiredField;
+import org.parceler.Parcel;
+
+import java.time.Instant;
+import java.util.List;
+
+@Parcel
+public class Announcement extends BaseModel implements DisplayItemsParent {
+    @RequiredField
+    public String id;
+    @RequiredField
+    public String content;
+    public Instant startsAt;
+    public Instant endsAt;
+    public boolean published;
+    public boolean allDay;
+    public Instant publishedAt;
+    public Instant updatedAt;
+    public boolean read;
+    public List<Emoji> emojis;
+    public List<Mention> mentions;
+    public List<Hashtag> tags;
+
+    @Override
+    public String toString() {
+        return "Announcement{" +
+                "id='" + id + '\'' +
+                ", content='" + content + '\'' +
+                ", startsAt=" + startsAt +
+                ", endsAt=" + endsAt +
+                ", published=" + published +
+                ", allDay=" + allDay +
+                ", publishedAt=" + publishedAt +
+                ", updatedAt=" + updatedAt +
+                ", read=" + read +
+                ", emojis=" + emojis +
+                ", mentions=" + mentions +
+                ", tags=" + tags +
+                '}';
+    }
+
+    public Status toStatus() {
+        Status s = new Status();
+        s.id = id;
+        s.mediaAttachments = List.of();
+        s.createdAt = startsAt != null ? startsAt : publishedAt;
+        if (updatedAt != null) s.editedAt = updatedAt;
+        s.content = s.text = content;
+        s.spoilerText = "";
+        s.visibility = StatusPrivacy.PUBLIC;
+        s.mentions = List.of();
+        s.tags = List.of();
+        s.emojis = List.of();
+        return s;
+    }
+
+    @Override
+    public String getID() {
+        return id;
+    }
+}