Update changelog content for preview 4. (#1028)

* Update changelog content for preview 4.

* Add more commits.

* Add PnP sample in changelog.

CHANGELOG.md

@@ -2,27 +2,52 @@
 
 ## 1.0.0-preview.4 (2020-08-10)
 
-- API breaking changes:
-  - `az_span.h`:
-    - `az_span_init()` is renamed to `az_span_create()`.
-    - `az_span_from_str()` is renamed to `az_span_create_from_str()`.
-    - `az_allocator_context` is renamed to `az_span_allocator_context`.
-    - Removed `az_pair_from_str()`.
-  - `az_context`:
-    - `key` and `value` are `const`.
-    - `az_context_with_expiration()` is renamed to `az_context_create_with_expiration()`.
-    - `az_context_with_value()` is renamed to `az_context_create_with_value()`.
-    - `az_context_app` is renamed to `az_context_application`.
-  - `az_credential_client_secret_init()` now takes fourth parameter, `authority`.
-  - `az_http_policy_retry_options`:
-    - `status_codes` now should be terminated by `AZ_HTTP_STATUS_CODE_END_OF_LIST`.
-    - `max_retries` is now `int32_t` instead of `int16_t`.
-  - `az_config.h`:
-    - `AZ_HTTP_REQUEST_URL_BUF_SIZE` renamed to `AZ_HTTP_REQUEST_URL_BUFFER_SIZE`.
-    - `AZ_HTTP_REQUEST_BODY_BUF_SIZE` renamed to `AZ_HTTP_REQUEST_BODY_BUFFER_SIZE`.
-    - `AZ_LOG_MSG_BUF_SIZE` renamed to `AZ_LOG_MESSAGE_BUFFER_SIZE`.
-  - `az_result`:
-    - `AZ_ERROR_HTTP_PLATFORM` renamed to `AZ_ERROR_HTTP_ADAPTER`.
+### New Features
+
+- Support for writing JSON to non-contiguous buffers.
+- Support for reading JSON from non-contiguous buffers.
+- Add support for national cloud auth URLs.
+
+### Breaking Changes
+
+- `az_span.h`:
+  - `az_span_init()` is renamed to `az_span_create()`.
+  - `az_span_from_str()` is renamed to `az_span_create_from_str()`.
+  - `az_allocator_context` is renamed to `az_span_allocator_context`.
+  - Removed `az_pair_from_str()`.
+- `az_context`:
+  - `key` and `value` are `const`.
+  - `az_context_with_expiration()` is renamed to `az_context_create_with_expiration()`.
+  - `az_context_with_value()` is renamed to `az_context_create_with_value()`.
+  - `az_context_app` is renamed to `az_context_application`.
+- `az_credential_client_secret_init()` now takes fourth parameter, `authority`.
+- `az_http_policy_retry_options`:
+  - `status_codes` now should be terminated by `AZ_HTTP_STATUS_CODE_END_OF_LIST`.
+  - `max_retries` is now `int32_t` instead of `int16_t`.
+- `az_config.h`:
+  - `AZ_HTTP_REQUEST_URL_BUF_SIZE` renamed to `AZ_HTTP_REQUEST_URL_BUFFER_SIZE`.
+  - `AZ_HTTP_REQUEST_BODY_BUF_SIZE` renamed to `AZ_HTTP_REQUEST_BODY_BUFFER_SIZE`.
+  - `AZ_LOG_MSG_BUF_SIZE` renamed to `AZ_LOG_MESSAGE_BUFFER_SIZE`.
+- `az_result`:
+  - `AZ_ERROR_HTTP_PLATFORM` renamed to `AZ_ERROR_HTTP_ADAPTER`.
+  - `AZ_ERROR_EOF` renamed to `AZ_ERROR_UNEXPECTED_END`.
+  - Removed `AZ_CONTINUE`.
+- `az_storage_blobs_blob_client`:
+  - `retry` field renamed to `retry_options` in `az_storage_blobs_blob_client_options`.
+  - Moved `az_context* context` parameter from `az_storage_blobs_blob_upload` into a public field on `az_storage_blobs_blob_upload_options`.
+- `az_json_writer`:
+  - `az_json_writer_get_json()` is renamed to `az_json_writer_get_bytes_used_in_destination()`.
+
+### Bug Fixes
+
+- Remove support for non-finite double values while parsing/formatting.
+- Use custom, portable implementation of IEEE 754 compliant `isfinite()` since some embedded platforms don't have it.
+
+### Other Changes and Improvements
+
+- Made `az_http_request` and related APIs to get URL, body, and headers, public.
+- Add and update IoT samples, including DPS.
+- Add samples for IoT Hub Plug and Play.
 
 ## 1.0.0-preview.3 (2020-07-20)