test(exec): add API tests for DetachKeys handling

Verify that POST /containers/{name}/exec correctly accepts an explicitly
empty DetachKeys field and that GET /exec/{id}/json returns the stored
value. Covers both the empty-string (disable detach) and non-empty cases.

Signed-off-by: Devesh B <98201065+DeveshB-1@users.noreply.github.com>

Author: DeveshB-1

test/apiv2/20-containers.at

@@ -913,4 +913,31 @@ t POST containers/create?platform=linux/amd64 \
 t POST containers/create?platform=linux/aarch64 \
   Image=$IMAGE \
   404
+
+# 28405: exec create must honour DetachKeys:"" (explicitly disable detach).
+# Previously the JSON decoder could not distinguish an absent field from an
+# explicitly-empty one, so DetachKeys:"" was silently ignored.
+podman run -d --name exec-detach-keys-test $IMAGE top
+
+# Explicitly empty DetachKeys disables detach - exec create must accept it.
+t POST containers/exec-detach-keys-test/exec \
+  Cmd='["true"]' \
+  DetachKeys='' \
+  201 \
+  .Id~[0-9a-f]\\{64\\}
+eid=$(jq -r '.Id' <<<"$output")
+t GET exec/$eid/json 200 .DetachKeys=''
+
+# A non-empty DetachKeys must be stored and returned by inspect.
+t POST containers/exec-detach-keys-test/exec \
+  Cmd='["true"]' \
+  DetachKeys='ctrl-c' \
+  201 \
+  .Id~[0-9a-f]\\{64\\}
+eid=$(jq -r '.Id' <<<"$output")
+t GET exec/$eid/json 200 .DetachKeys='ctrl-c'
+
+podman rm -f exec-detach-keys-test
+
+
 podman rmi -f $IMAGE