Enhance documentation in CommonTypes.fs

Added detailed comments for types and members, including
Accessor and Selection, to improve code clarity and
suggest more accurate naming. Clarified the purpose of
fields in the Selection type.

Author: usr3-1415

CommonTypes/CommonTypes.fs

@@ -18,11 +18,15 @@ type UserErrorSeverity =
     | WARNING
     | INFO
 
+/// Represents the kind of target (value, pointer, or array element) accessed during encoding/decoding.
+/// A more accurate name might be AccessTargetType.
 type SelectionType =
     | Value
     | Pointer
     | FixArray
 
+/// Represents a node in the access path from the function parameter to the current type.
+/// A more accurate name might be AccessStep.
 type Accessor =
     | ValueAccess of string * SelectionType * bool // selection identifier and its type
     | PointerAccess of string * SelectionType  * bool // selection identifier and its type
@@ -38,10 +42,12 @@ type Accessor =
         | PointerAccess _ -> Pointer
         | ArrayAccess _ -> FixArray
 
+/// Represents a path of accesses (fields, pointers, array elements) starting from a root object towards a nested element.
+/// A more accurate name might be AccessPath.
 type Selection = {
-    receiverId: string
-    receiverType: SelectionType
-    path: Accessor list
+    receiverId: string              // The name of the function parameter that holds the root ASN.1 type being processed (e.g., val, pVal, pVal1).
+    receiverType: SelectionType     // the access type of the function parameter
+    path: Accessor list             // in long fields, this is the path to the field
 } with
     static member emptyPath (receiverId: string) (receiverType: SelectionType): Selection =
         { Selection.receiverId = receiverId; receiverType = receiverType; path = []}