[Issue] Allow some SalesSequence data to be retrieved by extensions for customisatioons

[m2-assistant]

This issue is automatically created based on existing pull request: #40237: Allow some SalesSequence data to be retrieved by extensions for customisatioons

---

Description (*)

Being able to change the sequence generation for a specific entity type is a reasonably common request. The objective of this PR is to allow extensions to more easily modify this: currently, it is impossible without overriding the whole model (read: copy and paste, since everything is private).

This PR will allow extensions or vendors to change the format, for instance with an after plugin:

public function afterGetNextValue(
    \Magento\SalesSequence\Model\Sequence $subject,
    string $result
) {
    //If we're generating for an order, set its sequence to ECOM{STORE_ID}#{4 DIGIT INC. ID}
    if ('order' === $subject->getEntityType()) {
        return \sprintf('ECOM%d#%\'.04d', $subject->getStoreId(), $subject->calculateCurrentValue());
    }
    
    //Otherwise, passthrough
    return $result;
}

NB: this would probably be a good use case for some sort of expansion (having some di-defined array for entity types to calculate their values), but this is a good first step IMO.

Related Pull Requests

N/A

Fixed Issues (if relevant)

N/A

Manual testing scenarios (*)

This is a transparent API change: it should not change anything. Perhaps trying an after plugin like mentioned above.

Questions or comments

Unsure re: unit tests. I've added some, but they seem superfluous.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)