[FEATURE]: Add endorsement feature between identity tokens

[dhruvi-16-me]

Feature and its Use Cases

Overview

This feature will allow one identity token to endorse another identity token on-chain.

If a user owns an identity token, they should be able to endorse another user’s identity token. This endorsement should be stored on-chain and publicly verifiable.

What This Feature Should Do

• Allow an identity token owner to endorse another identity token
• Store the endorsement relationship on-chain
• Allow the original endorser to revoke their endorsement
• Allow anyone to check whether one identity has endorsed another

Basic Example

• Alice owns Identity Token 1
• Bob owns Identity Token 2
• Alice calls endorse(2)
• The contract records that 1 endorsed 2

Later:

• Alice can revoke the endorsement

Requirements

• A user must own an identity token to endorse someone
• A user cannot endorse themselves
• The same endorsement cannot be created twice
• Only the original endorser can revoke

Additional Context

No response

Code of Conduct

• I have joined the Discord server and will post updates there
• I have searched existing issues to avoid duplicates