Merge branch 'master' of https://github.com/nestjs/docs.nestjs.com

Author: kamilmysliwiec

content/graphql/unions-and-enums.md

@@ -114,7 +114,7 @@ export class Book {
 export type ResultUnion = Author | Book;
 ```
 
-Unions require an extra `__resolveType` field in the resolver map to determine which type the union should resolve to. Let's create a `ResultUnionResolver` class and define the `__resolveType` method:
+Unions require an extra `__resolveType` field in the resolver map to determine which type the union should resolve to. Also, note that the `ResultUnionResolver` class has to be registered as a provider in any module. Let's create a `ResultUnionResolver` class and define the `__resolveType` method. 
 
 ```typescript
 @Resolver('ResultUnion')

content/techniques/configuration.md

@@ -321,7 +321,7 @@ $ npm install --save joi
 $ npm install --save-dev @types/joi
 ```
 
-> warning **Notice** The latest version of `joi` requires you to be running Node v12 or later. For older versions of node, please install `v16.1.8`. This is mainly after the release of `v17.0.2` which causes errors during build time. For more information, please refer to [their documentation](https://hapi.dev/family/joi/?v=17.0.2#install) & this [github issue](https://github.com/hapijs/joi/issues/2266#issuecomment-571667769).
+> warning **Notice** The latest version of `joi` requires you to be running Node v12 or later. For older versions of node, please install `v16.1.8`. This is mainly after the release of `v17.0.2` which causes errors during build time. For more information, please refer to [their 17.0.0 release notes](https://github.com/sideway/joi/issues/2262).
 
 Now we can define a Joi validation schema and pass it via the `validationSchema` property of the `forRoot()` method's options object, as shown below:
 
@@ -344,7 +344,7 @@ import * as Joi from 'joi';
 export class AppModule {}
 ```
 
-By default, all schema keys are considered optional. Here, we set default values for `NODE_ENV` and `PORT` which will be used if we don't provide these variables in the environment (`.env` file or process environment). Alternatively, we can use the `required()` validation method to require that a value must be defined in the environment (`.env` file or process environment). In this case, the validation step will throw an exception if we don't provide the variable in the environment. See [Joi validation methods](https://hapi.dev/family/joi/?v=17.0.2#example) for more on how to construct validation schemas.
+By default, all schema keys are considered optional. Here, we set default values for `NODE_ENV` and `PORT` which will be used if we don't provide these variables in the environment (`.env` file or process environment). Alternatively, we can use the `required()` validation method to require that a value must be defined in the environment (`.env` file or process environment). In this case, the validation step will throw an exception if we don't provide the variable in the environment. See [Joi validation methods](https://joi.dev/api/?v=17.3.0#example) for more on how to construct validation schemas.
 
 By default, unknown environment variables (environment variables whose keys are not present in the schema) are allowed and do not trigger a validation exception. By default, all validation errors are reported. You can alter these behaviors by passing an options object via the `validationOptions` key of the `forRoot()` options object. This options object can contain any of the standard validation options properties provided by [Joi validation options](https://hapi.dev/family/joi/api/?v=17.0.2#anyvalidvalues---aliases-equal). For example, to reverse the two settings above, pass options like this: