Fix crash in ContentstackLogger and improve async/await handling for cache policies

- Updated CHANGELOG for version 2.5.1 with bug fixes related to ContentstackLogger and cache policies.
- Added a new test plan for iOS to ensure proper testing configurations.
- Removed outdated iOS test scheme files and replaced them with a new test plan.
- Enhanced async/await APIs to handle cache policies correctly, specifically converting `CachePolicy.cacheThenNetwork` to `CachePolicy.cacheElseNetwork`.
- Improved logging in ContentstackLogger to prevent crashes when using percent-encoded URLs as format strings.
- Added regression tests to ensure proper logging behavior and prevent crashes related to format specifiers.
- Updated documentation in README and CSDefinitions to clarify cache policy behaviors and logging practices.

Author: reeshika-h

CHANGELOG.md

@@ -1,5 +1,16 @@
 # CHANGELOG
 
+## v2.5.1
+
+### Date: 17-Aug-2026
+
+### Bug Fixes
+
+- Fixed a crash in `ContentstackLogger` caused by passing the log message to `NSLog` as the format string. Affects the default logger configuration (`logType = .nsLog`, `logLevel = .error`).
+- `CachePolicy.cacheThenNetwork` no longer crashes the `async`/`await` APIs; it is served as `CachePolicy.cacheElseNetwork`. The completion-handler APIs are unchanged.
+- `CachePolicy.networkElseCache` set per request now falls back to the cache on transport errors.
+- A response with neither data nor an error no longer leaves an `async` call suspended indefinitely.
+
 ## v2.5.0
 
 ### Date: 27-Jul-2026