Your main issue is actually a couple of space characters on these lines in your code:
--data '{
"commandOverride": ' "$NEXT_JOB_COMMANDS" '
}')
The 2nd single quote breaks out of the single-quoted string, which is the option argument to the --data option of curl. The space character just after the single quote ensures that the string in $NEXT_JOB_COMMANDS will be its own argument to curl, and you then add } (preceded by a newline) as an additional extra argument, probably confusing curl even more.
You could solve this by changing the middle line to
"commandOverride": '"$NEXT_JOB_COMMANDS"'
... but you could also use jq to insert your $NEXT_JOB_COMMANDS value into the form body (which would ensure that the resulting JSON body is well formed and valid).
If you want to pass a well-formed JSON document (your array) as a top-level key in a JSON document used with --data in your curl invocation, you may do as follows:
NEXT_JOB_COMMANDS='["sleep", "200s"]'
NEXT_JOB_ID=$(
formdata=$( jq -c -n --argjson commandOverride "$NEXT_JOB_COMMANDS" '$ARGS.named' ) &&
curl -s \
--header 'Content-Type: application/json' \
--data "$formdata" \
'http://localhost:5050/processes/gdalEcho/execution'
)
printf '%s\n' "$NEXT_JOB_ID"
Here, the shell variable formdata (which is local to the command substitution) will get the value
{"commandOverride":["sleep","200s"]}
This is created using jq, which will insert the given JSON fragment as the value for a commandOverride key.
A variant of the above allows you to avoid writing JSON entirely and instead stores your array as an array in the shell:
NEXT_JOB_COMMANDS=( 'sleep' '200s' )
NEXT_JOB_ID=$(
formdata=$(
jq -c -n '{ commandOverride: $ARGS.positional }' --args "${NEXT_JOB_COMMANDS[@]}"
) &&
curl -s \
--header 'Content-Type: application/json' \
--data "$formdata" \
'http://localhost:5050/processes/gdalEcho/execution'
)
printf '%s\n' "$NEXT_JOB_ID"
The above assumes a shell that has named arrays. For the /bin/sh shell, use set -- sleep 200s to set the list of positional parameters to the array elements, and then "$@" to insert that list after --args in the arguments to jq.