Development branch for v2.1.1

[chrisroadmap]

To release once there is a critical need

Please confirm that this pull request has done the following:

• [x] Tests added
• [x] Documentation added (where applicable)
• [x] Example added (either to an existing notebook or as a new notebook, where applicable)
• [x] Description in CHANGELOG.rst added
• [x] #115
• [x] #116
• [x] #117
• [x] #129
• [x] #130

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (4528252) 94.94% compared to head (39ba167) 95.08%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #118 +/- ## ========================================== + Coverage 94.94% 95.08% +0.13% ========================================== Files 19 19 Lines 732 732 Branches 105 105 ========================================== + Hits 695 696 +1 Misses 16 16 + Partials 21 20 -1 ``` | [Files](https://app.codecov.io/gh/OMS-NetZero/FAIR/pull/118?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=OMS-NetZero) | Coverage Δ | | |---|---|---| | [src/fair/fair.py](https://app.codecov.io/gh/OMS-NetZero/FAIR/pull/118?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=OMS-NetZero#diff-c3JjL2ZhaXIvZmFpci5weQ==) | `91.34% <ø> (+0.24%)` | :arrow_up: |

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