finagle-mysql: add missing newRichClient permutation

The `newRichClient` method in finagle-mysql does not
allow for both a `dest` and `label` to be passed as
a String, but is defined by the `newClient` method
which it proxies to. Let's add it.

JIRA Issues: CSL-11135

Differential Revision: https://phabricator.twitter.biz/D706140

CHANGELOG.rst

@@ -7,6 +7,13 @@ Note that ``PHAB_ID=#`` and ``RB_ID=#`` correspond to associated messages in com
 Unreleased
 ----------
 
+New Features
+~~~~~~~~~~~~
+
+* finagle-mysql: introduce `newRichClient(dest: String, label: String)` method, which removes the
+  need for extra boilerplate to convert the destination String to a `c.t.finagle.Name` when
+  specifying both `dest` and `label` in String form. ``PHAB_ID=D706140``
+
 Runtime Behavior Changes
 ~~~~~~~~~~~~~~~~~~~~~~~~
 

finagle-mysql/src/main/scala/com/twitter/finagle/Mysql.scala

@@ -41,6 +41,14 @@ trait MysqlRichClient { self: com.twitter.finagle.Client[Request, Result] =>
   def newRichClient(dest: Name, label: String): mysql.Client with mysql.Transactions =
     mysql.Client(newClient(dest, label), richClientStatsReceiver, supportUnsigned)
 
+  /**
+   * Creates a new `RichClient` connected to the logical
+   * destination described by `dest` with the assigned
+   * `label`. The `label` is used to scope client stats.
+   */
+  def newRichClient(dest: String, label: String): mysql.Client with mysql.Transactions =
+    mysql.Client(newClient(dest, label), richClientStatsReceiver, supportUnsigned)
+
   /**
    * Creates a new `RichClient` connected to the logical
    * destination described by `dest`.