docs: Add missing KDocs for exposed-dao InnerTableLink API

Add KDocs in `exposed-dao` to files relating to InnerTableLink.

exposed-dao/src/main/kotlin/org/jetbrains/exposed/dao/EntityClass.kt

@@ -333,7 +333,6 @@ abstract class EntityClass<ID : Comparable<ID>, out T : Entity<ID>>(
      * @sample org.jetbrains.exposed.sql.tests.shared.entities.EntityTests.Parent
      * @sample org.jetbrains.exposed.sql.tests.shared.entities.EntityTests.Children
      * @sample org.jetbrains.exposed.sql.tests.shared.entities.EntityTests.Child
-     *
      */
     infix fun <REF : Comparable<REF>> referencedOn(column: Column<REF>) = registerRefRule(column) { Reference(column, this) }
 

exposed-dao/src/main/kotlin/org/jetbrains/exposed/dao/InnerTableLink.kt

@@ -9,6 +9,18 @@ import org.jetbrains.exposed.sql.transactions.TransactionManager
 import kotlin.properties.ReadWriteProperty
 import kotlin.reflect.KProperty
 
+/**
+ * Class responsible for implementing property delegates of the read-write properties involved in a many-to-many
+ * relation, which uses an intermediate (join) table.
+ *
+ * @param table The intermediate table containing reference columns to both child and parent entities.
+ * @param sourceTable The [IdTable] associated with the source child entity.
+ * @param target The [EntityClass] for the target parent entity.
+ * @param _sourceColumn The intermediate table's reference column for the child entity class. If left `null`,
+ * this will be inferred from the provided intermediate [table] columns.
+ * @param _targetColumn The intermediate table's reference column for the parent entity class. If left `null`,
+ * this will be inferred from the provided intermediate [table] columns.
+ */
 @Suppress("UNCHECKED_CAST")
 class InnerTableLink<SID : Comparable<SID>, Source : Entity<SID>, ID : Comparable<ID>, Target : Entity<ID>>(
     val table: Table,
@@ -35,10 +47,12 @@ class InnerTableLink<SID : Comparable<SID>, Source : Entity<SID>, ID : Comparabl
         }
     }
 
+    /** The reference identity column for the child entity class. */
     val sourceColumn = _sourceColumn
         ?: table.columns.singleOrNull { it.referee == sourceTable.id } as? Column<EntityID<SID>>
         ?: error("Table does not reference source")
 
+    /** The reference identity column for the parent entity class. */
     val targetColumn = _targetColumn
         ?: table.columns.singleOrNull { it.referee == target.table.id } as? Column<EntityID<ID>>
         ?: error("Table does not reference target")

exposed-dao/src/main/kotlin/org/jetbrains/exposed/dao/References.kt

@@ -20,7 +20,7 @@ private fun checkReference(reference: Column<*>, factoryTable: IdTable<*>) {
 }
 
 /**
- * Class representing a table relation between 2 [Entity] classes, which is responsible for
+ * Class representing a table relation between two [Entity] classes, which is responsible for
  * retrieving the parent entity referenced by the child entity.
  *
  * @param reference The reference column defined on the child entity's associated table.
@@ -36,7 +36,7 @@ class Reference<REF : Comparable<REF>, ID : Comparable<ID>, out Target : Entity<
 }
 
 /**
- * Class representing an optional table relation between 2 [Entity] classes, which is responsible for
+ * Class representing an optional table relation between two [Entity] classes, which is responsible for
  * retrieving the parent entity optionally referenced by the child entity.
  *
  * @param reference The nullable reference column defined on the child entity's associated table.
@@ -53,7 +53,7 @@ class OptionalReference<REF : Comparable<REF>, ID : Comparable<ID>, out Target :
 
 /**
  * Class responsible for implementing property delegates of the read-only properties involved in a table
- * relation between 2 [Entity] classes, which retrieves the child entity that references the parent entity.
+ * relation between two [Entity] classes, which retrieves the child entity that references the parent entity.
  *
  * @param reference The reference column defined on the child entity's associated table.
  * @param factory The [EntityClass] associated with the child entity that references the parent entity.
@@ -70,7 +70,7 @@ internal class BackReference<ParentID : Comparable<ParentID>, out Parent : Entit
 
 /**
  * Class responsible for implementing property delegates of the read-only properties involved in an optional table
- * relation between 2 [Entity] classes, which retrieves the child entity that optionally references the parent entity.
+ * relation between two [Entity] classes, which retrieves the child entity that optionally references the parent entity.
  *
  * @param reference The nullable reference column defined on the child entity's associated table.
  * @param factory The [EntityClass] associated with the child entity that optionally references the parent entity.

exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/entities/EntityTests.kt

@@ -89,7 +89,7 @@ object EntityTestsData {
 
     class YEntity(id: EntityID<String>) : Entity<String>(id) {
         var x by YTable.x
-        val b by BEntity.backReferencedOn(XTable.y1)
+        val b: BEntity? by BEntity.backReferencedOn(XTable.y1)
         var content by YTable.blob
 
         companion object : EntityClass<String, YEntity>(YTable)