tm_textdecodebase64 function decodes a string that was previously Base64-encoded, and then interprets the result as characters in a specified character encoding.
Terraform uses the "standard" Base64 alphabet as defined in RFC 4648 section 4.
encoding_name argument must contain one of the encoding names or aliases recorded in the IANA character encoding registry. Terraform supports only a subset of the registered encodings, and the encoding support may vary between Terraform versions.
Terraform accepts the encoding name
UTF-8, which will produce the same result as
tm_textdecodebase64("SABlAGwAbABvACAAVwBvAHIAbABkAA==", "UTF-16LE") Hello World