#204 fixes numerous header classes to cast field value to string (since HeaderInterface::getFieldValue() specifies a return value of a string).

#182 fixes detecting base uri in Request. Now argv is used only for CLI request as a fallback to detect script filename.

#175 adds support for Content Security Policy Level 3 Header directives.

#200 adds support for additional directives in Content Security Policy header:

• block-all-mixed-content,
• require-sri-for,
• trusted-types,
• upgrade-insecure-requests.

#177 adds support for Feature Policy header.

#186 adds support for SameSite directive in Set-Cookie header.

#184 fixes responses for request through the proxy with HTTP/1.1 200 Connection established header.

#187 fixes infinite recursion on invalid header. Now InvalidArgumentException exception is thrown.

#188 fixes Client::setCookies method to properly handle array of SetCookie objects. Per documentation it should be allowed.

#189 fixes Headers::toArray method to properly handle headers of the same type. Behaviour was different depends how header has been attached (addHeader or addHeaderLine broken before).

#198 fixes merging options in Curl adapter. It was not possible to override integer-key options (constants) set via constructor with method setOptions.

#198 fixes allowed options type in Proxy::setOptions. Traversable, array or Zend\Config object is expected.

#198 fixes various issues with Proxy adapter.

#199 fixes saving resource to the file when streaming while client supports compression. Before, incorrectly, compressed resource was saved into the file.

#154 adds the method SetCookie::setEncodeValue(). By default, Set-Cookie
values are passed through urlencode(); when a boolean false is provided to
this new method, the raw value will be used instead.

#166 adds support for PHP 7.3.

#154 changes the behavior of SetCookie::fromString() slightly: if the parsed
cookie value is the same as the one passed through urldecode(), the
SetCookie header's $encodeValue property will be toggled off to ensure the
value is not encoded in subsequent serializations, thus retaining the
integrity of the value between usages.

#161 changes how the Socket and Test adapters aggregate headers. Previously,
they would ucfirst() the header name; now, they correctly leave the header
names untouched, as header names should be considered case-insensitive.

#156 changes how gzip and deflate decompression occur in responses, ensuring
that if the Content-Length header reports 0, no decompression is attempted,
and an empty string is returned.

#165 fixes detection of the base URL when operating under a CLI environment.

#149 provides fixes to Client::setUri() to ensure its status as a relative
or absolute URI is correctly memoized.

#162 fixes a typo in an exception message raised within Cookies::fromString().

#121 adds detection for non-numeric connection timeout values as well as
integer casting to ensure the timeout is set properly in both the Curl and
Socket adapters.