feat(GroupTheory/FiniteAbelian): prove that the restriction map is surjective

[xroblot]

Let G be a finite commutative group and let H be a subgroup. If M is a commutative monoid
such that G →* Mˣ and H →* Mˣ are both finite (this is the case for example if M is a
commutative domain), then any homomorphism H →* Mˣ can be extended to an homomorphism G →* Mˣ.

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[github-actions]

PR summary 88c480406b

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

+ Group.exponent_quotient_dvd
+ _root_.MonoidHom.restrictHomKerEquiv
+ _root_.MonoidHom.restrict_surjective
+ card_monoidHom_of_hasEnoughRootsOfUnity
+ exponent_submonoid_dvd
+ instance {L : Type*} [LeftCancelMonoid L] [Finite L] :
+ restrictHom
+ restrict_eq_one_iff

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[Ruben-VandeVelde]

Thanks

[xroblot]

Thanks

Thanks for the review!