cli: add lb4 relation command

docs/site/Relation-generator.md

@@ -0,0 +1,72 @@
+---
+lang: en
+title: 'Relation generator'
+keywords: LoopBack 4.0, LoopBack 4
+sidebar: lb4_sidebar
+permalink: /doc/en/lb4/Relation-generator.html
+---
+
+{% include content/generator-create-app.html lang=page.lang %}
+
+The models involved in the relation must exist before running this generator.
+
+### Synopsis
+
+Adds a new `Relation` between existing source and target models in a LoopBack
+application.
+
+```sh
+lb4 relation [options] [<idProperty>]
+```
+
+### Options
+
+TBD
+
+### Arguments
+
+`<idProperty>` - Name of the ID property that will be created in the source
+model. If not provided, the tool will use `id` as the default name when it
+prompts for the ID property name.
+
+### Interactive Prompts
+
+The tool will prompt you for:
+
+- **Relation `type` between models.** _(relationBaseClass)_ Prompts a list of
+  available relations to choose from as the type of the relation between the
+  source model and the target model. Supported relation types:
+
+  - hasMany
+  - hasOne
+  - belongsTo
+
+- **Name of the `source` model.** _(sourceModel)_ Prompts a list of available
+  models to choose from as the source model of the relation.
+
+- **Name of the `target` model.** _(targetModel)_ Prompts a list of available
+  models to choose from as the target model of the relation. Note: The selected
+  `source` model will not appear in the `target` model list.
+
+- **Name of the `ID property` in the source model.** _(Optional, default: `id`)_
+  Prompts for the ID property name (serves as the foreign key) in the source
+  model. Note: Leave blank to use the default.
+
+- **Name for the `property relation` in the source model.** TBD
+
+### Output
+
+Once all the prompts have been answered, the CLI will do the following:
+
+- Update source Model class as follows:
+  `/src/models/${sourceModel-Name}.model.ts`
+- Update target Model class as follows:
+  `/src/models/${targetModel-Name}.model.ts`
+- Update source Model Repository class as follows:
+  `/src/repositories/${sourceModel-Repository-Name}.repository.ts`
+- Update target Model Repository class as follows:
+  `/src/repositories/${targetModel-Repository-Name}.repository.ts`
+- Create a Controller for the new relation as follows:
+  `/src/controllers/{sourceModel}-{targetModel}.controller.ts`
+- Update `/src/controllers/index.ts` to export the newly created Controller
+  class.