slurmrestd - Add http_context_free_null_auth()

Add http_context_free_null_auth() to avoid duplicated code clearing
context->auth using http_context_set_auth().

Issue: 50189
diff --git a/src/slurmrestd/http.c b/src/slurmrestd/http.c
index 1086702..383c955 100644
--- a/src/slurmrestd/http.c
+++ b/src/slurmrestd/http.c
@@ -834,3 +834,13 @@
 
 	return old;
 }
+
+extern void http_context_free_null_auth(http_context_t *context)
+{
+	if (!context)
+		return;
+
+	xassert(context->magic == MAGIC);
+
+	FREE_NULL_REST_AUTH(context->auth);
+}
diff --git a/src/slurmrestd/http.h b/src/slurmrestd/http.h
index 0b2bb21..ec2aee7 100644
--- a/src/slurmrestd/http.h
+++ b/src/slurmrestd/http.h
@@ -144,4 +144,10 @@
  */
 extern void *http_context_set_auth(http_context_t *context, void *auth);
 
+/*
+ * Release and NULL auth pointer from context
+ * IN context - connection context
+ */
+extern void http_context_free_null_auth(http_context_t *context);
+
 #endif /* SLURMRESTD_HTTP_H */