Description / Feature proposal

CLI command to generate model TS file.

• The prompt asks:
  • name of the model
  • property name and type (repeating till user enter empty name for property name)
• The generated model.ts would look something like: https://github.com/strongloop/loopback-next/blob/0411811aa8348e31636fb0fe07b44dd18469280f/examples/todo/src/models/todo.model.ts

Outstanding questions

• Do we ask the user to select the base class? If yes, what are the selections? or it will always be Entity.
• What are the property types we support? Here is what we have in LB3:
  string
  number
  boolean
  object
  array
  date
  buffer

Acceptance Criteria

• Make a CLI prompt for model and its properties
  • For properties, ask for their name, their types and their default values
• The produced model should extend from Entity

User Experience

$ lb4 model
? Enter the model name: Customer
Let's add some Customer properties now. 

Enter an empty property name when done.
? Property name: customerId
? Property type:  (show a list of available types) string
? Required? (y/N) y
? Default value[leave blank for none]:

Let's add another Customer property.
Enter an empty property name when done.
? Property name: name
? Property type:  (show a list of available types) string
? Required? (y/N) y
? Default value[leave blank for none]:

At the end, src/models/customer.model.ts will be created.