message: Update the Azure Core changelog wording and content for the upcoming beta.4 release.
  Follow up to
  Went through the commits related to Azure Core between beta.3 and what we plan to ship for beta.4:
diff: - Added `Range` type to `Azure::Core::Http` namespace.
  - Added support for long-running operations with `Operation<T>`.
  - Added support for setting a custom transport adapter by implementing the method `std::shared_ptr<HttpTransport> ::AzureSdkGetCustomHttpTransport()`.
  -- Added default constructor to `DateTime`.
  -- Added `DateTime` supporting dates since 0001.
  +- Added interoperability between `std::chrono::system_clock` types and `DateTime`.
  +- Added default constructor to `DateTime` and support for dates since 0001.
  - Added Base64 encoding and decoding utility APIs to the `Azure::Core` namespace available from `azure/core/base64.hpp`.
  - Added `Http::Response<void>` template specialization.
  +- Added `GetHeadersAsString()` on the `Azure::Core::Http::Request` class.
  +- Added a `platform.hpp` header file for defining commonly used OS-specific `#define` constants.
  +- Added `IsCancelled()` on the `Azure::Core::Context` class.
  ### Breaking Changes
  -- Removed `DateTime::operator Duration()`.
  -- Removed `DateTime::Now()`.
  +- Removed `DateTime::operator Duration()`, `DateTime::Duration` typedef and `DateTime::Now()`.
  - Moved `Azure::Core::BearerTokenAuthenticationPolicy`, defined in `azure/core/credentials.hpp` to `Azure::Core::Http` namespace in `azure/core/http/policy.hpp` header.
  -- Removed option `AllowBeast` from `CurlTransportSSLOptions` in `CurlTransportOptions`.
  -- Changed default option `NoRevoke` from `CurlTransportSSLOptions` for the `CurlTransportOptions` to `true`. This disables the revocation list checking by default.
  - Changed type of `Token::ExpiresOn` to `DateTime`.
  -- Renamed exception `OperationCanceledException` to `OperationCancelledException`.
  -- Renamed methods from `Azure::Core::Context`.
  - - `IsCanceled` to `IsCancelled`
  - - `ThrowIfCanceled` to `ThrowIfCancelled`.
  +- Renamed exception `OperationCanceledException` to `OperationCancelledException` and `ThrowIfCanceled()` to `ThrowIfCancelled()` on the `Context` class.
  - Moved `Azure::Core::Version`, defined in `azure/core/version.hpp` to the `Azure::Core::Details` namespace.
  +- Changed `Azure::Core::AuthenticationException` to derive from `std::exception` instead of `std::runtime_error`.
  +- Changed the `BodyStream::Read` API from being a pure virtual function to non-virtual.
  +- Removed `CurlConnection`, `CurlConnectionPool`, `CurlSession`, and `CurlNetworkConnection` by making headers meant as implementation, private.
  +- Removed option `AllowBeast` from `CurlTransportSSLOptions` in `CurlTransportOptions`.
  +- Changed default option `NoRevoke` from `CurlTransportSSLOptions` for the `CurlTransportOptions` to `true`. This disables the revocation list checking by default.
  ### Bug Fixes
  - Fixed the Curl transport adapter connection pooling when setting options.
  - Fixed setting up the default transport adapter.
  +- Fixed linker error of missing pthread on Linux.
  +- Initialize class data members to avoid MSVC warning.
  +- Throw `Azure::Core::Http::TransportException` if `curl_easy_init()` returns a null handle.
  +
  +### Other changes and Improvements
  +
  +- Added support for distributing the C++ SDK as a source package via vcpkg.
  ## 1.0.0-beta.3 (2020-11-11)
  