add javadoc about key (de)serializers (#4673)

Author: pjfanning

src/main/java/com/fasterxml/jackson/databind/Module.java

@@ -197,6 +197,7 @@ public static interface SetupContext
          *
          * @param d Object that can be called to find deserializer for types supported
          *   by module (null returned for non-supported types)
+         * @see #addKeyDeserializers is used to register key deserializers (for Map keys)
          */
         public void addDeserializers(Deserializers d);
 
@@ -213,6 +214,7 @@ public static interface SetupContext
          *
          * @param s Object that can be called to find serializer for types supported
          *   by module (null returned for non-supported types)
+         * @see #addKeySerializers is used to register key serializers (for Map keys)
          */
         public void addSerializers(Serializers s);
 

src/main/java/com/fasterxml/jackson/databind/module/SimpleModule.java

@@ -321,6 +321,7 @@ protected SimpleModule setNamingStrategy(PropertyNamingStrategy naming) {
      * Possible earlier addition of a serializer for a given Class will be replaced.
      * <p>
      * NOTE: This method registers "default" (de)serializers only. See a note on precedence in class JavaDoc.
+     * @see #addKeySerializer(Class, JsonSerializer) is used to register key serializers (for Map keys)
      */
     public SimpleModule addSerializer(JsonSerializer<?> ser)
     {
@@ -345,6 +346,7 @@ public SimpleModule addSerializer(JsonSerializer<?> ser)
      * Possible earlier addition of a serializer for a given Class will be replaced.
      * <p>
      * NOTE: This method registers "default" (de)serializers only. See a note on precedence in class JavaDoc.
+     * @see #addKeySerializer(Class, JsonSerializer) is used to register key serializers (for Map keys)
      */
     public <T> SimpleModule addSerializer(Class<? extends T> type, JsonSerializer<T> ser)
     {
@@ -388,6 +390,7 @@ public <T> SimpleModule addKeySerializer(Class<? extends T> type, JsonSerializer
      * Possible earlier addition of a serializer for a given Class will be replaced.
      * <p>
      * NOTE: This method registers "default" (de)serializers only. See a note on precedence in class JavaDoc.
+     * @see #addKeyDeserializer(Class, KeyDeserializer)  is used to register key deserializers (for Map keys)
      */
     public <T> SimpleModule addDeserializer(Class<T> type, JsonDeserializer<? extends T> deser)
     {