FIX Throw exception when "value" is used to define indexes. Update docs.

docs/en/02_Developer_Guides/00_Model/12_Indexes.md

@@ -71,6 +71,11 @@ support the following:
     }
 ```
 
+<div class="alert" markdown="1">
+Please note that if you have previously used the removed `value` key to define an index's contents, SilverStripe will
+now throw an error. Use `columns` instead.
+</div>
+
 ## Complex/Composite Indexes
 For complex queries it may be necessary to define a complex or composite index on the supporting object. To create a 
 composite index, define the fields in the index order as a comma separated list. 

docs/en/04_Changelogs/4.0.0.md

@@ -1242,7 +1242,7 @@ use SilverStripe\ORM\DataObject;
  */
 class MyStagedModel extends SilverStripe\ORM\DataObject
 {
-    private staic $extensions = [
+    private static $extensions = [
         "SilverStripe\\ORM\\Versioning\\Versioned('StagedVersioned')"
     ];
 }
@@ -1971,6 +1971,7 @@ A very small number of methods were chosen for deprecation, and will be removed
 * `ChangeSet` and `ChangeSetItem` have been added for batch publishing of versioned dataobjects.
 * `DataObject.table_name` config can now be used to customise the database table for any record.
 * `DataObjectSchema` class added to assist with mapping between classes and tables.
+* `DataObject.indexes` now uses `columns` instead of `value` to define index contents.
 * `DBMoney` values are now treated as empty only if `Amount` field is null. If an `Amount` value
   is provided without a `Currency` specified, it will be formatted as per the current locale.
 * Removed `DatabaseAdmin#clearAllData()`. Use `DB::get_conn()->clearAllData()` instead

src/ORM/Connect/DBSchemaManager.php

@@ -558,8 +558,18 @@ abstract class DBSchemaManager
     protected function convertIndexSpec($indexSpec)
     {
         // Return already converted spec
-        if (!is_array($indexSpec) || !array_key_exists('type', $indexSpec) || !array_key_exists('columns', $indexSpec) || !is_array($indexSpec['columns'])) {
-            throw new \InvalidArgumentException(sprintf('argument to convertIndexSpec must be correct indexSpec, %s given', var_export($indexSpec, true)));
+        if (!is_array($indexSpec)
+            || !array_key_exists('type', $indexSpec)
+            || !array_key_exists('columns', $indexSpec)
+            || !is_array($indexSpec['columns'])
+            || array_key_exists('value', $indexSpec)
+        ) {
+            throw new \InvalidArgumentException(
+                sprintf(
+                    'argument to convertIndexSpec must be correct indexSpec, %s given',
+                    var_export($indexSpec, true)
+                )
+            );
         }
 
         // Combine elements into standard string format