staticTargeting: add flag to switch default to true

[nathantournant]

What does this PR do?

• Adds new functionality
• Alters existing functionality
• Fixes a bug
• Improves documentation or testing

Please briefly describe your changes as well as the motivation behind them:

• Now places the default value for staticTargeting to a flag in the controller's config map.

Code Quality Checklist

• The documentation is up to date.
• My code is sufficiently commented and passes continuous integration checks.
• I have signed my commit (see Contributing Docs).

Testing

• I leveraged continuous integration testing
  • by depending on existing unit tests or end-to-end tests.
  • by adding new unit tests or end-to-end tests.
• I manually tested the following steps:
  • Deploy the controller with the staticTargetingDefault field set to false, launch a disruption with staticTargeting unspecified, check out the description
  • Do all of those combinations (flag false/true, staticTargeting field unspecified/false/true) and assert you have the expected results.
  • locally.
  • as a canary deployment to a cluster.

[ptnapoleon]

Why did this have to become a pointer again? The default for a bool is already false, no?

[nathantournant]

afaik go bool unmarshalling doesn't make a difference between false and empty value -- if it's not a pointer.
Setting a default to true would be overridden by a missing/defaulted field that would be interpreted as a false

[nathantournant]

This PR aims to allow true to be a possible default value based on the chart
This value, if set, needs to not be overridden by an empty one
edit: fixed the title, sorry about the confusion

[ptnapoleon]

I see. There is another option, I think? At the cost of some wordier unmarshaling, we can avoid making this be a pointer everywhere.

If we make the type of StaticTargeting not bool, but a custom type: type StaticTargetingFlag bool, we can add a custom Unmarshal for that type that uses the chart-defined default when empty.

[nathantournant]

I tried a few things, hoping this would work; without a new dedicated struct type for the field -which would not really help- the UnmarshalJSON function is not called on an empty value 😞
I'm afraid the pointer is unavoidable there

[ptnapoleon]

Is it..... too late to change this field to "Targeting" with the options of "dynamic,static,empty", where empty uses the default? Representing three states by using a pointer to a bool feels wrong