The intrinsic function
Fn::Join appends a set of values into a single value, separated
by the specified delimiter. If a delimiter is the empty string, the set of values are concatenated with no
"Fn::Join" : [ "
comma-delimited list of
values ] ]
The value you want to occur between fragments. The delimiter will occur between fragments only. It will not terminate the final value.
The list of values you want combined.
The combined string.
"Fn::Join" : [ ":", [ "a", "b", "c" ] ]
This example returns: "a:b:c".