Add a Tag to a Post

[hannahhall]

As an author I would like to be able to associate one or more Tags with one of my Posts so that readers can easily see the Post topics at a glance.

Given the author is viewing Post details
When they select the Manage Tags option
Then they should be presented with a selection of Tags options to associate with the Post

Given the author has selected the Tags they wish to associate with a Post
When they click the Save button
Then the association should be saved to the database
And the user should be directed to the Post details page
And the selected Tags should be displayed on the Post details page