feat: add support for network related flags on create, clone, and upgrade

Also add some tests to cover all the network-related functionality.

tests/test_helper.bash

@@ -70,3 +70,17 @@ assert_output() {
   fi
   assert_equal "$expected" "$output"
 }
+
+# ShellCheck doesn't know about $output from Bats
+# shellcheck disable=SC2154
+assert_output_contains() {
+  local input="$output"
+  local expected="$1"
+  local count="${2:-1}"
+  local found=0
+  until [ "${input/$expected/}" = "$input" ]; do
+    input="${input/$expected/}"
+    found=$((found + 1))
+  done
+  assert_equal "$count" "$found"
+}