Arch meeting/add api response design

.gitignore

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 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
+
+/.vscode

docs/schulcloud-server/Api.md

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+# API design
+
+## nest.js
+
+In nest.js all apis are defined in controllers.
+Usually the api follows the following syntax:
+
+```typescript
+/api/v3/<resource>
+```
+
+- Each controller is responsible for a specific resource. 
+- The controller is responsible for the routing and the validation of the request.
+- The controller calls a service to handle the request. 
+- The service is responsible for the business logic. 
+- The service calls a repository to access the database. 
+- The repository is responsible for the database access.
+
+## Responses
+
+When returning a response like this:
+
+```typescript
+    @ApiOperation({ summary: 'Create a new element on a card.' })
+	@ApiExtraModels(
+		ExternalToolElementResponse,
+		FileElementResponse,
+		LinkElementResponse,
+		RichTextElementResponse,
+		SubmissionContainerElementResponse
+	)
+	@ApiResponse({
+		status: 201,
+		schema: {
+			oneOf: [
+				{ $ref: getSchemaPath(ExternalToolElementResponse) },
+				{ $ref: getSchemaPath(FileElementResponse) },
+				{ $ref: getSchemaPath(LinkElementResponse) },
+				{ $ref: getSchemaPath(RichTextElementResponse) },
+				{ $ref: getSchemaPath(SubmissionContainerElementResponse) },
+			],
+		},
+	})
+	@ApiResponse({ status: 400, type: ApiValidationError })
+	@ApiResponse({ status: 403, type: ForbiddenException })
+	@ApiResponse({ status: 404, type: NotFoundException })
+	@Post(':cardId/elements')
+	async createElement(
+		@Param() urlParams: CardUrlParams,
+		@Body() bodyParams: CreateContentElementBodyParams,
+		@CurrentUser() currentUser: ICurrentUser
+	): Promise<AnyContentElementResponse> {
+		const { type, toPosition } = bodyParams;
+		const element = await this.cardUc.createElement(currentUser.userId, urlParams.cardId, type, toPosition);
+		const response = ContentElementResponseFactory.mapToResponse(element);
+
+		return response;
+	}
+```
+
+We want to use decorators to explain the intent of the response.  
+The `@ApiOperation` decorator is used to define the summary.  
+The `@ApiResponse` decorator is used to define the response.  
+The `@ApiExtraModels` decorator is used to define the response models.  
+
+The final response should either be an javascript Object or an array.
+We do not return primitives like `string` or `boolean`.
+
+Swagger will automatically generate the response schema from the response object.

static/CNAME

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+documentation.dbildungscloud.dev