Added User Data Model

"There are as many choices for a user data model as there are different
registration forms on the web; we’ll go with a distinctly minimalist
approach. Users of our demo app will have a unique integer identifier
called id, a publicly viewable name (of type string), and an email
address (also a string) that will double as a username. A summary of the
data model for users appears in Figure 2.2."
Added User Data Model

"There are as many choices for a user data model as there are different
registration forms on the web; we’ll go with a distinctly minimalist
approach. Users of our demo app will have a unique integer identifier
called id, a publicly viewable name (of type string), and an email
address (also a string) that will double as a username. A summary of the
data model for users appears in Figure 2.2."