Function format_is_packet 

pub fn format_is_packet(
    source: &str,
    destination: &str,
    path: &[&str],
    data: &str,
) -> String

Format an APRS packet for transmission to APRS-IS.

Builds the source>destination,path:data\r\n string. The path elements are joined with commas.

Note: the APRS-IS server ignores / overwrites the Q-construct element in the path if one isn’t present (it adds its own based on how the packet arrived). For explicit Q-construct handling use crate::format_is_packet_with_qconstruct.