A shared utxo is a coin owned by several users. Each user can spend its share of the coin, but only if he provides a change output with remaining shares to the other users.
This can be achieved on the Liquid Network thanks to introspection opcodes OP_INSPECTOUTPUTSCRIPTPUBKEY and OP_INSPECTOUTPUTVALUE contraining the spender to provide a change output with a specific scriptPubKey and value.
## Building the covenant
Each stakeholder is represented by:
- the amount of the coin he owns
- a list of tapscript leaves letting to spend this amount
The function sharedCoinTree will build the covenant from an array of stakeholders. It recursively build all the subtrees expected by the change output and add it to the stakeholder's leaves.