Terraform: Render special characters from typical query string (like '=', '&') in a variable assignment

Question

It seems that Terraform is either rendering the intended query string value "... = ..", with &#61, which messes up the URL call.

I tried to escape the \= in the string assignment, and errors, with 'The symbol "=" is not a valid escape sequence selector'.

I also tried format("%s %s %s", "...", "=", "...."). Same rendering with &#61.

Any ideas? Newbie, here with terraform. Thanks, in advance.