fix(contracts): subscriptions count in payment service addSubscriptions

[maximopalopoli]

Description

This PR modifies the addSubscriptions behavior to only add to the active subscriptions counter when the address was not already subscribed.

How to test

Start the anvil node and deploy the anvil contracts with:

make ethereum_package_start

To fetch the current value of the active subscriptions counter:

cast call 0x922D6956C99E12DFeB3224DEA977D0939758A1Fe "activeSubscriptionsAmount()(uint256)"

To call the addSubscriptions method:

cast send 0x922D6956C99E12DFeB3224DEA977D0939758A1Fe \                                     
  "addSubscriptions(address[],uint256)" \
  "[0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266,0x70997970C51812dc3A010C7d01b50e0d17dc79C8,0x3C44CdDdB6a900fa2b585dd299e03d12FA4293BC]" \
 <UTC_SECONDS_TIMESTAMP> \
  --private-key 0xdbda1821b80551c9d65939329250298aa3472ba22feea921c0cf5d620ea67b97

The array of addresses can be changed.

The thing to test is that the counter does not change when the addresses are already subscribed.

Type of change

Please delete options that are not relevant.

• New feature
• Bug fix
• Optimization
• Refactor

Checklist

• “Hotfix” to testnet, everything else to staging
• Linked to Github Issue
• This change depends on code or research by an external entity
  • Acknowledgements were updated to give credit
• Unit tests added
• This change requires new documentation.
  • Documentation has been added/updated.
• This change is an Optimization
  • Benchmarks added/run
• Has a known issue
  • Link to the open issue addressing it
• If your PR changes the Operator compatibility (Ex: Upgrade prover versions)
  • This PR adds compatibility for operator for both versions and do not change crates/docs/examples
  • This PR updates batcher and docs/examples to the newer version. This requires the operator are already updated to be compatible