Adding SIG metadata description

Author: bari12

docs/project_organisation.md

@@ -65,7 +65,7 @@ Each SIG must define
 Currently there are two Rucio special interest groups:
 
   - Quality of Service (QoS)
-  - Metadata
+  - [Metadata](sig_metadata.md)
 
 ## Contributors / Developers
 

docs/sig_metadata.md

@@ -0,0 +1,27 @@
+---
+id: sig_metadata
+title: SIG Metadata
+---
+
+## Objective
+
+The purpose of this SIG is to reach out to communities who are either already using 
+Rucio's metadata functionality or interested in using it, to ascertain if the 
+functionality currently provided in this area is sufficient for their current and 
+expected future use cases. This information will be distilled into the form of a 
+small report, where, if missing functionality is identified, the report will serve 
+to aggregate any similar requests and prioritise them, with the goal of delivering 
+a tentative roadmap to guide development.
+
+## Expected End-Date
+
+End of 2023
+
+## Means to achieve the objective
+
+A general mattermost channel + ad hoc meetings with interested communities either 
+over Zoom or asynchronously over Mattermost.
+
+## Convener
+
+[Rob Barnsley](https://github.com/robbarnsley)