[#26] object: Remove Link message

After updating the structure of SplitHeader and StorageGroup messages, the
Link header field is no longer needed. This commit removes the field and
message Link as no longer used.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

object/types.proto

@@ -17,8 +17,6 @@ message Attribute {
 }
 
 message ExtendedHeader {
-    // Link to other objects
-    Link Link = 1;
     // Redirect not used yet
     refs.Address Redirect = 2;
     // Attribute is a set of K-V object attributes
@@ -62,26 +60,6 @@ message IntegrityHeader {
     bytes ChecksumSignature = 2;
 }
 
-message Link {
-    enum Type {
-        Unknown      = 0;
-        // Parent object created during object transformation
-        Parent       = 1;
-        // Previous object in the linked list created during object transformation
-        Previous     = 2;
-        // Next object in the linked list created during object transformation
-        Next         = 3;
-        // Child object created during object transformation
-        Child        = 4;
-        // Object that included into this storage group
-        StorageGroup = 5;
-    }
-    // Type of link
-    Type type  = 1;
-    // ID is an object identifier, is a valid UUIDv4
-    bytes ID = 2;
-}
-
 // SplitHeader groups information about spawning the object through a payload splitting.
 message SplitHeader {
     // Parent carries identifier of the origin object.

proto-docs/object.md

@@ -33,7 +33,6 @@
     - [ExtendedHeader](#object.ExtendedHeader)
     - [Header](#object.Header)
     - [IntegrityHeader](#object.IntegrityHeader)
-    - [Link](#object.Link)
     - [Object](#object.Object)
     - [PublicKey](#object.PublicKey)
     - [SplitHeader](#object.SplitHeader)
@@ -381,7 +380,6 @@ Attribute groups the parameters of the object attributes.
 
 | Field | Type | Label | Description |
 | ----- | ---- | ----- | ----------- |
-| Link | [Link](#object.Link) |  | Link to other objects |
 | Redirect | [refs.Address](#refs.Address) |  | Redirect not used yet |
 | Attribute | [Attribute](#object.Attribute) |  | Attribute is a set of K-V object attributes |
 | SplitHeader | [SplitHeader](#object.SplitHeader) |  | Split carries the position of the object in the split hierarchy. |
@@ -418,18 +416,6 @@ Header groups the information about the NeoFS object.
 | ChecksumSignature | [bytes](#bytes) |  | ChecksumSignature is an user's signature of checksum to verify if it is correct |
 
 
-<a name="object.Link"></a>
-
-### Message Link
-
-
-
-| Field | Type | Label | Description |
-| ----- | ---- | ----- | ----------- |
-| type | [Link.Type](#object.Link.Type) |  | Type of link |
-| ID | [bytes](#bytes) |  | ID is an object identifier, is a valid UUIDv4 |
-
-
 <a name="object.Object"></a>
 
 ### Message Object
@@ -491,21 +477,6 @@ SplitHeader groups information about spawning the object through a payload split
  <!-- end messages -->
 
 
-<a name="object.Link.Type"></a>
-
-### Link.Type
-
-
-| Name | Number | Description |
-| ---- | ------ | ----------- |
-| Unknown | 0 |  |
-| Parent | 1 | Parent object created during object transformation |
-| Previous | 2 | Previous object in the linked list created during object transformation |
-| Next | 3 | Next object in the linked list created during object transformation |
-| Child | 4 | Child object created during object transformation |
-| StorageGroup | 5 | Object that included into this storage group |
-
-
  <!-- end enums -->