Create global initial version constant and use it for initializing all the versioned entities

[DubeySandeep]

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. This issue focus on defining a global constant initial entity version (Which will be zero) and use this constant in all the files.

Few places in the codebase where we have hardcoded the initial version:

• exp_domain.py
• question_editor.py for question initialization.
• topic_domain.py

Pointers (to start with):

• Check all the models which are made out of VersionedModel.
• Check how the new models are created for these versionsedModel
• Add constant for the version number.

[seanlip]

This is suitable for a good first issue (since it can be done with limited context), but is on the slightly harder side so is probably better taken up by contributors who have previous experience with refactoring a codebase. The plan should be:

• Define an INITIAL_ENTITY_VERSION constant in feconf.py.
• Find all places where that version is set manually when creating domain objects, and change that to use the default initial entity version instead. (There may be other places besides the ones @DubeySandeep listed.)

Note: If you see any conflicts (e.g. one place uses 0 and another uses 1 for the initial entity version), please comment on this issue and add links to those places so that we can advise on what to do here. Thanks!

Additional note: See #20301 for a prior PR that wasn't completed (but that might be a good starting point).

[Chiranjeev-Kartik]

I would be happy to work on this issue. Please assign it to me.

[seanlip]

@Chiranjeev-Kartik Per the guidance at https://github.com/oppia/oppia/wiki/Contributing-code-to-Oppia#choosing-a-good-first-issue, please provide an explanation of what your PR will do (with names of files you're changing, what you plan to change in each file, etc.). If it looks good, we can assign you to this issue.

For this issue I would suggest making a list of the specific places in the code you would change per my previous comment, explain how you found them, and how you know that that's the complete list.

Please also follow the other instructions on that wiki page if you have not yet done so. Thanks!

[kumarankit999]

Should i work on this