Create an example of mcp server using token exchange

[yrobla]

Use an exisiting MCP server in our registry (candidate is oci-registry) to showcase the functionality of using exchanged tokens to gain access to an API.
Details of the flow can be seen at: https://docs.google.com/document/d/1fr92govq9VkOVCAdc6mpca-RSwit_Ydo5BqErpitM_E/edit?tab=t.0#heading=h.ejm8xurc8dei

Tasks:

•  Modify oci-registry mcp server to accept authorization bearer tokens
•  Provide an example using Okta for using this application with token exchange (login via Okta and getting access to an oci registry). Demo to clients
•  Create blogpost for that feature