[CLI] Prevent usage of already used keywords

Description / Steps to reproduce / Feature proposal

When using the CLI I can create a model named Entity, or Model. The model is generated but no warning will be emitted (this keyword is already used by Loopback).

Current Behavior

The model/controller/datasource/... is generated.

import {Model, model, property} from '@loopback/repository';

@model()
export class Model extends Model {
  constructor(data?: Partial<Model>) {
    super(data);
  }
}

Expected Behavior

Multiple options here:

1. add warnings in the creation process
2. prevent the component (model/controller/...) from being created
   1. by retrying
   2. by exiting
3. modify the generated file , for a model e.g:

import * as repository from '@loopback/repository';

@repository.model()
export class Model extends repository.Model {
  constructor(data?: Partial<Model>) {
    super(data);
  }
}

Keywords to consider

For controllers: nothing (overwriting existing controllers is already handled)

For datasources: nothing (overwriting existing datasources is already handled)

For models:

• Entity
• Model

For repositories:

• Repository

For services: ?

For openapi: nothing

Anything else ?

Acceptance criteria

Add a Yeoman prompt validator to reject model/repository/controller names that are the same as one of the built-in ones. This way, when a user enters invalid name, Yeoman will print an error and repeat the prompt.

• Enhance ArtifactGenerator.promptArtifactName() to allow subclasses (specific generators) to further customize the validation rules for artifact name. For example, we can introduce a protected property that subclasses can override.

  https://github.com/strongloop/loopback-next/blob/752db84f3e6f4984c35c2fc65f54eacae23e002e/packages/cli/lib/artifact-generator.js#L60

For each of the following generators, provide validation rule that will reject problematic names:

• lb4 controller
• lb4 datasource
• lb4 interceptor
• lb4 model
• lb4 observer
• lb4 relation
• lb4 repository
• lb4 service

🎆 Hacktoberfest 2020

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