As per the Utility Argument Syntax convention

Each option name should be a single alphanumeric character (the alnum character classification) from the portable character set. The -W (capital-W) option shall be reserved for vendor options.

Multi-digit options should not be allowed.

The first - argument that is not an option-argument should be accepted as a delimiter indicating the end of options. Any following arguments should be treated as operands, even if they begin with the '' character.

Current behavior: The action will execute the filepath like this:
/shared/username.sh -payload {"actionType":"custom",....}

Expected behavior: Following the convention, the payload should be sent as

/shared/username.sh  --payload {...}