opa fmt: rewrite = for non-unification cases

[anderseknert]

What part of OPA would you like to see improved?

Since the stated best practice is to use := for assignment and == for comparison, and only use = for unification, it would be nice if opa fmt rewrote Rego policies to follow this convention.

Describe the ideal solution

Smart detection of unification.

Describe a "Good Enough" solution

Convert at least simple cases of assignment and comparison.

[stale]

This issue has been automatically marked as inactive because it has not had any activity in the last 30 days.

[anderseknert]

Closing in favor of #4508, where we'll try to compile all ideas for the next iteration of opa fmt (and where this is included).