Adding hash to Custom

[andrea-pasquale]

Closes #1100.

Checklist:

• [x] Reviewers confirm new code works as expected.
• [x] Tests are passing.
• [x] Coverage does not decrease.
• [x] Documentation is updated.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 50.87%. Comparing base (ed8b3cc) to head (5550a10).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1101 +/- ## ========================================== + Coverage 50.84% 50.87% +0.03% ========================================== Files 63 63 Lines 2903 2905 +2 ========================================== + Hits 1476 1478 +2 Misses 1427 1427 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibolab/pull/1101/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qiboteam/qibolab/pull/1101/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `50.87% <100.00%> (+0.03%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam#carryforward-flags-in-the-pull-request-comment) to find out more.

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