docs: writing queries guide

README.md

@@ -99,6 +99,7 @@ Welcome! Here you will find everything you need to know to get started with and
 
 ## How-to
 
+- [Write Queries](documentation/how-to/write-queries.livemd)
 - [Test Resources](documentation/how-to/test-resources.livemd)
 - [Authorize Access to Resources](documentation/how-to/authorize-access-to-resources.livemd)
 - [Encrypt Attributes](documentation/how-to/encrypt-attributes.livemd)

documentation/dsls/DSL-Ash.Resource.md

@@ -2190,6 +2190,7 @@ identity :full_name, [:first_name, :last_name]
 | [`pre_check?`](#identities-identity-pre_check?){: #identities-identity-pre_check? } | `boolean` | `false` | Whether or not this identity is validated to be unique in a before_action hook. |
 | [`pre_check_with`](#identities-identity-pre_check_with){: #identities-identity-pre_check_with } | `module` |  | Validates that the unique identity provided is unique in a before_action hook. |
 | [`description`](#identities-identity-description){: #identities-identity-description } | `String.t` |  | An optional description for the identity |
+| [`field_names`](#identities-identity-field_names){: #identities-identity-field_names } | `atom \| list(atom)` |  | The field names to hold errors when unique identity is violated. |
 | [`message`](#identities-identity-message){: #identities-identity-message } | `String.t` |  | An error message to use when the unique identity would be violated |
 | [`all_tenants?`](#identities-identity-all_tenants?){: #identities-identity-all_tenants? } | `boolean` | `false` | Whether or not this identity is unique across all tenants. If the resource is not multitenant, has no effect. |