extend model options documentation for properties 'underscored' and 'underscoredAll' (#7528)

lib/model.js

@@ -670,8 +670,8 @@ class Model {
    * @param {Boolean}                 [options.omitNull] Don't persist null values. This means that all columns with null values will not be saved
    * @param {Boolean}                 [options.timestamps=true] Adds createdAt and updatedAt timestamps to the model.
    * @param {Boolean}                 [options.paranoid=false] Calling `destroy` will not delete the model, but instead set a `deletedAt` timestamp if this is true. Needs `timestamps=true` to work
-   * @param {Boolean}                 [options.underscored=false] Converts all camelCased columns to underscored if true
-   * @param {Boolean}                 [options.underscoredAll=false] Converts camelCased model names to underscored table names if true
+   * @param {Boolean}                 [options.underscored=false] Converts all camelCased columns to underscored if true. Will not affect timestamp fields named explicitly by model options and will not affect fields with explicitly set `field` option
+   * @param {Boolean}                 [options.underscoredAll=false] Converts camelCased model names to underscored table names if true. Will not change model name if freezeTableName is set to true
    * @param {Boolean}                 [options.freezeTableName=false] If freezeTableName is true, sequelize will not try to alter the model name to get the table name. Otherwise, the model name will be pluralized
    * @param {Object}                  [options.name] An object with two attributes, `singular` and `plural`, which are used when this model is associated to others.
    * @param {String}                  [options.name.singular=Utils.singularize(modelName)]