add meta.md doc

Author: Mr-Leshiy

docs/src/architecture/08_concepts/signed_doc/cddl/additional_meta.cddl

@@ -0,0 +1,11 @@
+additional_fields = {
+  ? "ref" => reference_type,
+  ? "template" => reference_type,
+  ? "reply" => reference_type,
+  ? "section" => text,
+  ? "collabs" => [+any],
+}
+
+reference_type = UUID / [UUID, UUID]
+
+UUID = #6.37(bytes)

docs/src/architecture/08_concepts/signed_doc/cddl/signed_doc_meta.cddl

@@ -10,10 +10,14 @@ signed_doc_meta = {
   3 => text / int, ; "content type"
   ? "Content-Encoding" / "content-encoding" => "br", ; payload content encoding
 
+  ~meta.additional_fields,
+
   * metadata-key => metadata-value
 }
 
 metadata-key = int / text
 metadata-value = any
 
-UUID = #6.37(bytes)
+UUID = #6.37(bytes)
+
+;# include additional_meta as meta

docs/src/architecture/08_concepts/signed_doc/meta.md

@@ -1 +1,65 @@
-Something
+
+<!-- markdownlint-disable max-one-sentence-per-line code-block-style -->
+??? note "Additional Metadata fields: `additional_meta.cddl`"
+
+    ```CDDL
+    {{ include_file('src/architecture/08_concepts/signed_doc/cddl/additional_meta.cddl', indent=4) }}
+    ```
+<!-- markdownlint-enable max-one-sentence-per-line code-block-style -->
+
+## `ref` Document Reference
+
+This is a reference to another document.
+The purpose of the `ref` will vary depending on the document [`type`](./spec.md#type).
+
+The `ref` can be either a single [UUID] or a [CBOR] Array of Two [UUID].
+
+If the `ref` is a single [UUID], it is a reference to the document of that [`id`](./spec.md#id).
+If the `ref` is a [CBOR] array, it has the form `[<id>,<ver>]` where:
+
+* `<id>` = the [UUID] of the referenced documents [`id`](./spec.md#id)
+* `<ver>` = the [UUID] of the referenced documents [`ver`](./spec.md#ver).
+
+## `template` Template Reference
+
+If the document was formed from a template, this is a reference to that template document.
+The format is the same as the [CBOR] Array form of [`ref`](#ref-document-reference).
+
+It is invalid not to reference the template that formed a document.
+If this is missing from such documents, the document will itself be considered invalid.
+
+Template references must explicitly reference both the Template Document ID, and Version.
+
+## `reply` Reply Reference
+
+This is a reply to another document.
+The format is the same as the [CBOR] Array form of [`ref`](#ref-document-reference).
+
+`reply` is always referencing a document of the same type, and that document must `ref` reference the same document `id`.
+However, depending on the document type, it may reference a different `ver` of that `id`.
+
+## `section` Section Reference
+
+This is a reference to a section of a document.
+It is a CBOR String, and contains a [JSON Path] identifying the section in question.
+
+Because this metadata field uses [JSON Path], it can only be used to reference a document whose payload is [JSON].
+
+## `collabs` Authorized Collaborators
+
+This is a list of entities other than the original author that may also publish versions of this document.
+This may be updated by the original author, or any collaborator that is given "author" privileges.
+
+The latest `collabs` list in the latest version, published by an authorized author is the definitive
+list of allowed collaborators after that point.
+
+The `collabs` list is a [CBOR] Array.
+The contents of the array are TBD.
+
+However, they will contain enough information such that each collaborator can be uniquely identified and validated.
+
+*Note: An Author can unilaterally set the `collabs` list to any list of collaborators.
+It does NOT mean that the listed collaborators have agreed to collaborate, only that the Author
+gives them permission to.*
+
+This list can impact actions that can be performed by the `Proposal Action Document`.

docs/src/architecture/08_concepts/signed_doc/spec.md

@@ -48,8 +48,10 @@ It fully inherits an original [COSE] design and specifies the details of differe
 
 To uniquely specify a Catalyst Signed Document type, version etc., as it was mentioned before,
 a list of different metadata fields is specified.
+
 Also as you can see from the specification,
 it is allowed to add any number of additional metadata fields, which could be specified for each `type` of document.
+A full list of considered additional metadata fields defined [here](./meta.md).
 
 All these fields will be encoded as the [COSE] `protected` header