V7.0 dev colnamesDS

[timcadman]

Instructions & checklist for PR author

Description of changes

• Refactored colnamesDS to include checks (that will be removed from the client-side function.
• Added two helper functions in R/utils: .loadServersideObject() and .checkClass()
• These helper functions can be reused when refactoring other functions

Refactor instructions

• Replaced x <- eval(parse(text = x.name), envir = parent.frame()) with x <- .loadServersideObject(x)
• If necessary, check the class of the object using .checkClass()

Testing instructions

• Writen server-side unit tests for unhappy flow
• Run devtools::test(filter = "smk-|disc|arg") and check it passes
• Run devtools::check(args = '--no-tests') and check it passes (we run tests separately to skip performance checks)
• Run devtools::build() and check it builds without errors

Instructions & checklist for PR reviewers

• Code review
• Run devtools::test(filter = "smk-|disc|arg") and check it passes
• Run devtools::check(args = '--no-tests') and check it passes (we run tests separately to skip performance checks)
• Run devtools::build() and check it builds without errors