docs: add docs

Author: temarusanov

README.md

@@ -1,6 +1,21 @@
 # NestJS Response Structure
 
-GraphQL Types and interfaces for great response
+GraphQL Types and interfaces for great response. The library provides types for the structured display of responses to the client.
+
+## Features
+
+- Structured types covered with TypeScript
+- `data` and `error` fields only without any extensions
+- Detailed error information including uuid, description, code, message and stacktrace
+- Stacktrace can be disabled in any time. Example: production mode
+
+**Success response:**
+
+![image](https://i.ibb.co/BgXh0sC/photo-2021-11-24-16-55-43.jpg)
+
+**Error response:**
+
+![image](https://i.ibb.co/vzVJstR/photo-2021-11-24-16-57-17.jpg)
 
 ## Installation
 
@@ -10,6 +25,70 @@ Requires node version >=12.х
 npm i --save nestjs-response-structure
 ```
 
+## Documentation
+
+### Setting up
+
+1. Add filter to your NestJS project. It will catch all errors and return formatted error.
+
+```ts
+// main.ts
+
+import { ResponseFilter } from 'nestjs-response-structure'
+
+async function bootstrap(): Promise<void> {
+    const app = await NestFactory.create(AppModule)
+
+    app.useGlobalFilters(new ResponseFilter({}))
+
+    // your code here
+}
+```
+
+2. Extend your GraphQL type. You can also make it abstract.
+
+```ts
+// user.type.ts
+
+@ObjectType({ isAbstract: true })
+class UserPayloadType {
+    @Field(() => ID)
+    id: string
+
+    @Field()
+    name: string
+}
+
+@ObjectType('User')
+export class UserType extends ResponsePayloadType(UserPayloadType) {}
+```
+
+3. Throw your custom errors. Filter uses NestJS exceptions and take `message` and `description` from NestJS error response.
+
+
+```ts
+// user.service.ts
+
+const user = await userRepository.findOne({ id })
+
+if (!user) {
+    throw new NotFoundException({
+        message: 'USER_NOT_FOUND',
+        description: `User not found with id ${id}`,
+    })        
+}
+
+return user
+```
+
+### Error type fields
+
+- `id` auto generated UUID to quickly find an entry in logs.
+- `message` is used for code message responses. For example, if frontend have a localization by the error code message.
+- `code` HTTP status codes.
+- `description` is used for development. The field helps to find out a more detailed reason for the error.
+- `stack` error stacktrace. You can disable this function in the filter constructor.
+
 ## License