Use page token to stop pagination in tests

The tests were breaking pagination loops when key_versions was empty,
but a valid VSS implementation may return the final batch of results
alongside an empty page token. Use the page token as the stop
condition instead, which better matches the API contract.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: benthecarman

rust/api/src/kv_store_tests.rs

@@ -395,12 +395,11 @@ pub trait KvStoreTestSuite {
 				},
 			};
 
-			if current_page.key_versions.is_empty() {
-				break;
-			}
-
 			all_key_versions.extend(current_page.key_versions);
-			next_page_token = current_page.next_page_token;
+			match current_page.next_page_token {
+				Some(token) if !token.is_empty() => next_page_token = Some(token),
+				_ => break,
+			}
 		}
 
 		if let Some(k1_response) = all_key_versions.iter().find(|kv| kv.key == "k1") {
@@ -446,13 +445,12 @@ pub trait KvStoreTestSuite {
 				},
 			};
 
-			if current_page.key_versions.is_empty() {
-				break;
-			}
-
 			assert!(current_page.key_versions.len() <= page_size as usize);
 			all_key_versions.extend(current_page.key_versions);
-			next_page_token = current_page.next_page_token;
+			match current_page.next_page_token {
+				Some(token) if !token.is_empty() => next_page_token = Some(token),
+				_ => break,
+			}
 		}
 
 		let unique_keys: std::collections::HashSet<String> =
@@ -492,12 +490,11 @@ pub trait KvStoreTestSuite {
 				Some(next_page_token) => ctx.list(Some(next_page_token), None, None).await?,
 			};
 
-			if current_page.key_versions.is_empty() {
-				break;
-			}
-
 			all_key_versions.extend(current_page.key_versions);
-			next_page_token = current_page.next_page_token;
+			match current_page.next_page_token {
+				Some(token) if !token.is_empty() => next_page_token = Some(token),
+				_ => break,
+			}
 		}
 
 		let unique_keys: std::collections::HashSet<String> =
@@ -545,14 +542,11 @@ pub trait KvStoreTestSuite {
 				Some(token) => ctx.list(Some(token), Some(1), Some("pfx_".to_string())).await?,
 			};
 
-			if current_page.key_versions.is_empty() {
-				assert_eq!(current_page.next_page_token, Some(String::new()));
-				break;
-			}
-
-			assert_eq!(current_page.key_versions.len(), 1);
 			all_keys.extend(current_page.key_versions.into_iter().map(|kv| kv.key));
-			next_page_token = current_page.next_page_token;
+			match current_page.next_page_token {
+				Some(token) if !token.is_empty() => next_page_token = Some(token),
+				_ => break,
+			}
 		}
 
 		// Should get prefixed keys in reverse creation order (newest first), excluding "other".
@@ -579,16 +573,15 @@ pub trait KvStoreTestSuite {
 				None => ctx.list(None, None, None).await?,
 				Some(next_page_token) => ctx.list(Some(next_page_token), None, None).await?,
 			};
-			if current_page.key_versions.is_empty() {
-				break;
-			}
-
 			assert!(
 				current_page.key_versions.len() < vss_arbitrary_page_size_max as usize,
 				"Page size exceeds the maximum allowed size"
 			);
 			all_key_versions.extend(current_page.key_versions);
-			next_page_token = current_page.next_page_token;
+			match current_page.next_page_token {
+				Some(token) if !token.is_empty() => next_page_token = Some(token),
+				_ => break,
+			}
 		}
 
 		assert_eq!(all_key_versions.len(), total_kv_objects as usize);