add new java file for enum mustache template

Author: wing328

modules/swagger-codegen/src/main/resources/Java/libraries/common/modelInnerEnum.mustache

@@ -0,0 +1,20 @@
+  /**
+   * {{^description}}Gets or Sets {{{name}}}{{/description}}{{#description}}{{{description}}}{{/description}}
+   */
+  public enum {{#datatypeWithEnum}}{{.}}{{/datatypeWithEnum}}{{^datatypeWithEnum}}{{classname}}{{/datatypeWithEnum}} {
+    {{#allowableValues}}{{#enumVars}}@SerializedName({{#isInteger}}"{{/isInteger}}{{#isDouble}}"{{/isDouble}}{{#isLong}}"{{/isLong}}{{#isFloat}}"{{/isFloat}}{{{value}}}{{#isInteger}}"{{/isInteger}}{{#isDouble}}"{{/isDouble}}{{#isLong}}"{{/isLong}}{{#isFloat}}"{{/isFloat}})
+    {{{name}}}({{{value}}}){{^-last}},
+
+    {{/-last}}{{#-last}};{{/-last}}{{/enumVars}}{{/allowableValues}}
+
+    private {{datatype}} value;
+
+    {{#datatypeWithEnum}}{{.}}{{/datatypeWithEnum}}{{^datatypeWithEnum}}{{classname}}{{/datatypeWithEnum}}({{datatype}} value) {
+      this.value = value;
+    }
+
+    @Override
+    public String toString() {
+      return String.valueOf(value);
+    }
+  }