Code quality

[kamushadenes]

Several fixes that shouldn't affect any functionality, but that greatly improve code quality and readability.

Also, added golangci-lint config and workflow to prevent future issues, as well as SCA security checks.

Changes

• Replaced deprecated code
• Removed unused code
• Avoid lots of unnecessary allocations by using more direct methods
• Avoid lots of unnecessary conversions / casts of the same type
• Added missing body closures
• Added explicit tags to some structs that where YAML / JSON marshaled
• Overall makes the code more idiomatic

[laskoviymishka]

This one is too big to merge, we avoid such monstrous PR-s, having more that 20 files in diff is already very dangerous.
In a meantime there is a lot of nice changes, if you extract them in separate PR-s and keep them narrow in terms of scope - it would be possible to merge relatively easy.

There is couple changes that I would prefer to rollback:

1. All changes in library/go, this code is semi-owned by a transfer, in a fact it's more like a copy-paste style vendored code.
2. All changes in comments, no need to all those dot's, see here for rationaly
3. All json and yaml tags for entities inside pkg/providers, this would make version upgrades much more complicated for no good reason.
4. Linter and CI-code, this better to make under chore: Setup linter inside CI #177 epic, there is already some linting in place, but it's not automated in CI.

[laskoviymishka]

nice impr, better to extract in separate PR.