feat: add constants (#61)

src/main/java/io/github/doocs/im/constant/Condition.java

+package io.github.doocs.im.constant;
+
+/**
+ * 条件
+ *
+ * @author bingo
+ * @since 2021/11/9 16:40
+ */
+public class Condition {
+    /**
+     * 属性的或条件
+     */
+    public static final String ATTRS_OR = "AttrsOr";
+
+    /**
+     * 属性的与条件
+     */
+    public static final String ATTRS_AND = "AttrsAnd";
+
+    /**
+     * 标签的或条件
+     */
+    public static final String TAGS_OR = "TagsOr";
+
+    /**
+     * 标签的与条件
+     */
+    public static final String TAGS_AND = "TagsAnd";
+
+    private Condition() {
+
+    }
+}

src/main/java/io/github/doocs/im/constant/MsgComplete.java

+package io.github.doocs.im.constant;
+
+/**
+ * 消息是否全部拉取
+ *
+ * @author bingo
+ * @since 2021/11/9 16:37
+ */
+public class MsgComplete {
+    /**
+     * 已全部拉取
+     */
+    public static final int YES = 1;
+
+    /**
+     * 未全部拉取，需要记录拉
+     */
+    public static final int NO = 0;
+
+    private MsgComplete() {
+
+    }
+}

src/main/java/io/github/doocs/im/constant/SendMsgControl.java

+package io.github.doocs.im.constant;
+
+/**
+ * 消息发送控制项
+ *
+ * @author bingo
+ * @since 2021/11/9 16:32
+ */
+public class SendMsgControl {
+    /**
+     * 该条消息不计入未读数
+     */
+    public static final String NO_UNREAD = "NoUnread";
+
+    /**
+     * 该条消息不更新会话列表
+     */
+    public static final String NO_LAST_MSG = "NoLastMsg";
+
+    /**
+     * 该条消息的接收方对发送方设置的免打扰选项生效（默认不生效）
+     */
+    public static final String WITH_MUTE_NOTIFICATIONS = "WithMuteNotifications";
+
+    private SendMsgControl() {
+
+    }
+}