feat: add Parse.Object.saveAllSettled to support more robust saving of multiple Parse Objects

[simonaberry]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

Related issue: #494 #799 #1433 and this StackOverflow issue

Parse.Object.saveAll can create data consistency issues. Because saveAll (which uses the /batch endpoint) will reject if any of the save items in the list fails, you can end up with 19 saved objects and 1 unsaved object. If the cause of the failure was a network delay, then the saveAll will automatically retry, with all 20 objects again - which leads to duplicated objects on the server.

Approach

Parse.Object.saveAllSettled fixes this problem, by using the Promise.allSettled method and individual, staggered object. save() calls - which waits for the saving of all the objects in the list to resolve or reject, then only tries to resave any objects that didn't successfully save the first time.

TODOs before merging

• Add tests
• Add entry to changelog
• ?support passing of context?

[parse-github-assistant]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[simonaberry]

I tried to do some test, but could not figure out how the xhr.open.mock.calls bit works ... bit out of my depth there

[mtrezza]

Could you please create an issue or reference an existing issue for this PR.

[mtrezza]

Closing as the issue has been identified as merely a docs issue and transferred to docs repo as parse-community/docs#859.