feat: abra release now asks for a release note (!393)

This implements coop-cloud/organising#540 by checking if a`release/next` file exists and if so moves it to `release/<tag>`. When no release notes exists it prompts for them.

Reviewed-on: coop-cloud/abra#393
Reviewed-by: moritz <moritz.m@local-it.org>
Co-authored-by: p4u1 <p4u1_f4u1@riseup.net>
Co-committed-by: p4u1 <p4u1_f4u1@riseup.net>

tests/integration/helpers/file.bash

@@ -0,0 +1,24 @@
+_mkfile() {
+  run bash -c "echo $2 > $1"
+  assert_success
+}
+
+_mkfile_remote() {
+  run $ABRA app run "$TEST_APP_DOMAIN" app "bash -c \"echo $2 > $1\""
+  assert_success
+}
+
+_mkdir() {
+  run bash -c "mkdir -p $1"
+  assert_success
+}
+
+_rm() {
+  run rm -rf "$1"
+  assert_success
+}
+
+_rm_remote() {
+  run "$ABRA" app run "$TEST_APP_DOMAIN" app rm -rf "$1"
+  assert_success
+}