Enhance BaseToggle with additional enabled/disabled toggle methods

[robrap]

Enhance BaseToggle with additional methods.

Add the following:

• is_disabled: Returns not is_enabled.
• is_toggled_on: Returns is_enabled.
• is_toggled_off: Returns not is_enabled.

This should make a variety of conditions more readable when ENABLE_ or DISABLE_ are in the toggle name.

Example 1: is_disabled

# BEFORE: slightly less readable
not SOME_FEATURE_TOGGLE.is_enabled()

# AFTER: more clear
SOME_FEATURE_TOGGLE.is_disabled()  

Example 2: is_toggled_off

# BEFORE: brain twister
not DISABLE_SOME_FEATURE.is_enabled()

# AFTER: more clear
DISABLE_SOME_FEATURE.is_toggled_off()  

Notes:

• For a DISABLE_FEATURE toggle, the toggle is off when the feature is on, so we use _toggle_ in the method name is_toggled_off to clearly refer to the toggle and not the feature.
• For docs, possibly add an “Other ways to check a toggle” (or something like that) after https://github.com/openedx/edx-toggles/blob/master/docs/how_to/implement_the_right_toggle_type.rst#accessing-toggles?
• Similar change is needed for CourseWaffleFlag in edx-platform, which is slightly different because it takes an argument for is_enabled.

Questions:

• Is this in fact simpler to understand? Are there better options?
  • We've decided to move forward

Work required:

• feat:added toggle methods to basemodel  #293
• Update docs (see notes)
• Update CourseWaffleFlag in edx-platform (see notes).

[Theo-flux]

Hello @robrap can i work on this ?

[robrap]

That would be great @Theo-flux. Let me know if you have any questions.

[robrap]

@Theo-flux: As part of this work, it might be good to share the proposal and get feedback, in case anyone has any better ideas on naming. Would you want to start a discussion in discuss.openedx.org about this proposal?

[Theo-flux]

That would be great @Theo-flux. Let me know if you have any questions
Let me go through the codebase. I'll get back to you.

[Theo-flux]

@Theo-flux: As part of this work, it might be good to share the proposal and get feedback, in case anyone has any better ideas on naming. Would you want to start a discussion in discuss.openedx.org about this proposal?

Just opened a discussion on openedx now https://discuss.openedx.org/t/ideas-for-naming-methods-in-a-class/10630/1

[robrap]

Thank you! Also, it will be pretty quick to search/replace your code if someone suggest a good change in the next day or two, so feel free to start the PR in parallel.

[Theo-flux]

OK @robrap sounds great! Let me set things up from end. I'll let you know when I have question(s) to ask. Thanks

[Theo-flux]

@robrap kindly check my PR. Not all checks passed. I already filled the contribution form. I am yet to get the document so I can sign on it. Thanks!

[Theo-flux]

@robrap I am still yet to receive the CLA document. I hope this is not an error

[robrap]

@Theo-flux: Once the CLA gets worked out (which it will), I can do the review. Thank you!

[robrap]

[inform] This ticket is available for work. @Theo-flux was almost able to complete this in this PR: #293. It just needs some minor work to get it over the line. Thanks again @Theo-flux for your contribution.