Set app label via instantiation of historical records

[uhurusurfa]

Description

Provide the ability to override the app_label Meta attribute on the generated history model.
This functionality alreay exists using the register method. The mechanism for this feature is identical
to the way it is implemented in the register method by allowing passing an app name in the instantiation.
The code change adds an additional instantiation parameter to the init method for the HistoricalRecords class
and then uses this parameter if provided in the get_meta_data method.

Related Issue

Fixes #485

Motivation and Context

It is often desirable to have the app_label different to the base model so that the history models can be directed to a different database.
This enhances security of the audit trail and can be used in situations where there is a need ot reduce the load on the main application database.
This also provides the same functionality between the "register()" and "HistoricalRecords()" mechanism for initiating audit trails on base models.

How Has This Been Tested?

A unit test was included to test this change. It only affects the setting of a Meta class attribute and does not functionally change the app code.

Screenshots (if appropriate):

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.
• All new and existing tests passed.
  NOTE: There is 1 test that failed but failed even without the code change

[codecov-io]

Codecov Report

Merging #486 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #486      +/-   ##
==========================================
+ Coverage   97.19%   97.22%   +0.02%     
==========================================
  Files          16       16              
  Lines         713      720       +7     
  Branches       94       95       +1     
==========================================
+ Hits          693      700       +7     
  Misses         10       10              
  Partials       10       10

Impacted Files	Coverage Δ
simple_history/models.py	99.21% <100%> (ø)	⬆️
simple_history/registry_tests/tests.py	95.87% <100%> (+0.17%)	⬆️

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[rossmechanic]

Looks good to me! Want to add this change to CHANGES.rst and add your name to AUTHORS.rst and then I'll merge? @uhurusurfa

[rossmechanic]

Also @uhurusurfa what test failed?

[uhurusurfa]

Also @uhurusurfa what test failed?

Here is the fail trace extract minus the middle bits that do not help much:

`ERROR: test_transaction_rolls_back_if_bulk_history_create_fails (simple_history.tests.tests.test_utils.BulkCreateWithHistoryTransactionTestCase)

Traceback (most recent call last):
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/db/backends/sqlite3/base.py", line 328, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.IntegrityError: UNIQUE constraint failed: django_content_type.app_label, django_content_type.model

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/test/testcases.py", line 211, in call
self._post_teardown()
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/test/testcases.py", line 926, in _post_teardown
self._fixture_teardown()
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/test/testcases.py", line 967, in _fixture_teardown
connections[db_name]._test_serialized_contents
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/db/backends/base/creation.py", line 133, in deserialize_db_from_string
obj.save()
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/core/serializers/base.py", line 223, in save
....
....
....
File "/Users/chris/git/django-simple-history/.tox/py36-djangotrunk/lib/python3.6/site-packages/django/db/backends/sqlite3/base.py", line 328, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: UNIQUE constraint failed: django_content_type.app_label, django_content_type.model
`

[uhurusurfa]

@rossmechanic - have etched my name in the anals of simple history and updted the changes file

[rossmechanic]

Weird that you saw that error locally. Since CI passed, I'm happy to merge. Thanks for this change!