docs: Add documentation for the experimental columnOverride feature.

docs/06-concepts/21-experimental.md

@@ -30,9 +30,114 @@ $ serverpod generate --experimental-features=all
 
 The current options you can pass are:
 
-| **Feature**     | Description                                                                         |
-| :-------------- | :---------------------------------------------------------------------------------- |
-| **all**         | Enables all available experimental features.                                        |
+| **Feature**        | Description                                                    |
+| :----------------- | :------------------------------------------------------------- |
+| **all**            | Enables all available experimental features.                   |
+| **columnOverride** | Allows overriding the column name for a field in the database. |
+
+## Column name override
+
+Serverpod allows you to specify the column name for a field in the database overriding the default use of the model property name as the column name.
+This can be useful when the column names in the database are not following the same naming convention as the model properties.
+
+### Usage
+
+To override the column name, use the `column` keyword in the `fields` configuration of your [model](database/models) file to specify the column name in the database.
+
+```yaml
+class: User
+table: users
+fields:
+  userName: String, column=user_name
+```
+
+### Restrictions
+
+- **ID Field**: The `id` field cannot have a column name override.
+- **Unique**: The column name must be unique within the model.
+- **Relations**: The `column` keyword is only allowed on the [foreign key field](database/relations/one-to-one#with-an-id-field) of a relation.
+
+### Relations
+
+You can use the `column` keyword to override the name of the foreign key field in a relation.
+
+```yaml
+# Employee
+class: Employee
+table: employee
+fields:
+  name: String
+  departmentId: int, relation(name=department_employees, parent=department), column=fk_employee_department_id
+
+# Department
+class: Department
+table: department
+fields:
+  name: String
+  employees: List<Employee>?, relation(name=department_employees)
+```
+
+This is also supported when the field is used in an index.
+
+```yaml
+# Contractor
+class: Contractor
+table: contractor
+fields:
+  name: String
+  serviceIdField: int?, column=fk_contractor_service_id
+  service: Service?, relation(field=serviceIdField)
+indexes:
+  contractor_service_unique_idx:
+    fields: serviceIdField
+    unique: true
+
+# Service
+class: Service
+table: service
+fields:
+  name: String
+  description: String?
+```
+
+### Inheritance
+
+The column name override is also supported when using [inheritance](models#inheritance) and will be applied to all child classes. This is especially useful when you have multiple database tables that share similar column names. This allows you to define a parent class as a regular [model](../get-started/models-and-data) and specify additional fields in the child classes defined as [table models](database/models).
+
+```yaml
+# Entity
+class: Entity
+fields:
+  name: String
+  createdAt: DateTime, default=now, column=created_at
+  updatedAt: DateTime, default=now, column=updated_at
+
+# Employee
+class: Employee
+extends: Entity
+table: employee
+fields:
+  departmentId: int, relation(name=department_employees, parent=department), column=fk_employee_department_id
+
+# Department
+class: Department
+extends: Entity
+table: department
+fields:
+  employees: List<Employee>?, relation(name=department_employees)
+
+# Contractor
+class: Contractor
+extends: Entity
+table: contractor
+fields:
+  serviceIdField: int?, column=fk_contractor_service_id
+  service: Service?, relation(field=serviceIdField)
+indexes:
+  contractor_service_unique_idx:
+    fields: serviceIdField
+    unique: true
+```
 
 ## Exception monitoring
 
@@ -158,7 +263,7 @@ void main() {
 
 Serverpod provides support for registering **shutdown tasks**—asynchronous operations that are executed when the server is shutting down. This is useful for performing cleanup operations such as saving application state or releasing external resources.
 
-Shutdown tasks are executed *after* the server has stopped accepting new requests, but *before* the Redis and database connections are closed.
+Shutdown tasks are executed _after_ the server has stopped accepting new requests, but _before_ the Redis and database connections are closed.
 
 All registered shutdown tasks are executed concurrently, and the server waits for all tasks to complete before fully shutting down. If any task fails, the error is logged, but it does not prevent the server from shutting down.