Allow static metadata to be defined

[maleck13]

What

Sometimes it would be useful to be able define some static metadata that could then be used in decisions.

Example:

metadata:
  rbac:
    static:
      "accounting": ["allow1", "allow2"]

Ideally this would become part of the auth.metadata so it could be used in the predicates for example

sudo code:

request.header["x-mcp-toolname"] in auth.metadata.rbac[auth.identity.group]