FIX #10274: Create global initial version constant and use it for initializing all the versioned entities

[Patrick-Haselof]

Overview

1. This PR fixes or fixes part of Create global initial version constant and use it for initializing all the versioned entities #10274 .
2. This PR does the following: According to the Issue "Currently, the initial value for the version number is hardcoded in the domain layer for all the entities which make it open for any entity to add incorrect initial version number", following by suggesting the creation of a Global Variable to act as a consultable constant that all files that require the initial version number can access. It was also pointed that there may be more files that needed refactoring, so after doing what was suggested and created a constant called INITIAL_ENTITY_VERSION in feconf.py, I tried to find more files that needed to be modified. The files controllers and domain have been fully searched:

Modified files:

• exp_domain.py
• topic_domain.py
• collection_domain.py
• exp_fetchers_test.py
• question_domain.py
• story_domain.py
• subtopic_page_domain.py

Found that needed refactoring but needs to be looked into/Uncertain of how to properly modify:

• skill_domain.py
• stats_domain.py

This Issue fix is pure refactoring and no logic has been modified or added

Essential Checklist

Please follow the instructions for making a code change.

• I have linked the issue that this PR fixes in the "Development" section of the sidebar.
• I have checked the "Files Changed" tab and confirmed that the changes are what I want to make.
• I have written tests for my code.
• The PR title starts with "Fix #bugnum: " or "Fix part of #bugnum: ...", followed by a short, clear summary of the changes.
• I have assigned the correct reviewers to this PR (or will leave a comment with the phrase "@{{reviewer_username}} PTAL" if I can't assign them directly).

Proof that changes are correct

This is a simple refactoring work. Since the code logic has not been modified there is no proof.

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[oppiabot]

Hi @Patrick-Haselof, can you complete the following:

1. The body of this PR is missing the overview section, please update it to include the overview.
   Thanks!

[oppiabot]

Assigning @lkbhitesh07 for the first pass review of this PR. Thanks!

[github-actions]

Hi! @Patrick-Haselof Welcome to Oppia! Could you please follow the instructions here and sign the CLA Sheet to get started? You'll need to do this before we can accept your PR. Thanks!

[Patrick-Haselof]

This was an accident, I meant to push to my Fork

[oppiabot]

Hi @Patrick-Haselof, can you complete the following:

1. The body of this PR is missing the overview section, please update it to include the overview.
   Thanks!

[github-actions]

Hi! @Patrick-Haselof Welcome to Oppia! Could you please follow the instructions here and sign the CLA Sheet to get started? You'll need to do this before we can accept your PR. Thanks!

[Patrick-Haselof]

This PR is trying to merge from my Branch instead of my Fork. I tried editing and even creating a new PR, didn't manage to do it, so for now I'll leave this open.

[lkbhitesh07]

Hey @Patrick-Haselof, thanks for the changes. I would suggest to follow this comment mentioned on the issue and then make the changes to this PR, this is the pattern we are currently following.
Thanks