Ensure that latest() is idempotent.

[jeking3]

Description

Two records with the same history_date cannot be retrieved idempotently with latest(). The get_latest_by meta property uses history_date which means if multiple records have the same timestamp, the resulting record returned by the database is not predictable (it would depend on the behavior of the database). If history_date is not indexed the result may be different than if it is indexed, for example (this was observed in #729). The meta property should include sorting by history_id.

Related Issue

This closes #861

Motivation and Context

When latest() is not idempotent, the behavior can change over time (for example adding an index).

How Has This Been Tested?

The unit tests exercise this behavior.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have run the make format command to format my code
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have added my name and/or github handle to AUTHORS.rst
• I have added my change to CHANGES.rst
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #862 (183716b) into master (be7b8b6) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #862   +/-   ##
=======================================
  Coverage   97.67%   97.68%           
=======================================
  Files          18       19    +1     
  Lines         990      994    +4     
  Branches      151      151           
=======================================
+ Hits          967      971    +4     
  Misses         10       10           
  Partials       13       13           

Impacted Files	Coverage Δ
simple_history/models.py	97.86% <ø> (ø)
simple_history/registry_tests/tests.py	95.87% <ø> (ø)
...lmodelwithcustomattrforeignkey_options_and_more.py	100.00% <100.00%> (ø)

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[jeking3]

One job in PR #863 just failed because of this issue. This code is not in that PR.

[sarathak]

code look good.