Current implementation clears _headers when request was sent. If the
user added custom request headers, they will be lost and the redirected
request will not contain them. This commit changes the scope of cleanup
so that the headers survive redirects but don't survive connection
reuse.
The client always appends "Basic" to the authorization header, however there are other auth schemes that can be used: https://developer.mozilla.org/en-US/docs/Web/HTTP/Authentication
For example "Bearer" when using OAuth.
This PR adds a `setAuthorizationType` method to the HTTPClient which allows this scheme to be configured by the caller. Authorization type is set to "Basic" by default so this will have no impact on existing usecases.
In [HTTPClient](https://github.com/espressif/arduino-esp32/tree/master/libraries/HTTPClient), if the `Transfer-Encoding` header is set to `identity`, an error (Transfer-Encoding not supported) will occur.
HTTPClient will consider the request as `identity` if the `Transfer-Encoding` header is not set. But it is also defined a response with `identity` explicitly set in the `Transfer-Encoding` header (ref:[MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Transfer-Encoding)).
This pull request will allow the request to be processed normally even when `identity` is explicitly set.
When connecting using transportTraits, the CA and client certificates are ignored after the initial _client->connect() is called. This is because on connect, WiFiClientSecure will call start_ssl_client with _CA_Cert and other cert options set to null unless setCACert, setCertificate etc. are called before connect. Running _transportTraits->verify after connect therefore does exactly nothing. It's easy to verify that this is the case by passing a CACert to HTTPClient with verbose logging enabled - the logs will say "WARNING: Use certificates for a more secure communication!" which is only present when both PSK and CA are null. This change fixes the issue.
If two headers with overlapping names are added while replace == true, like in:
```cpp
http.addHeader("api_token", "pMXFOLpinQqajaRQJYMeWObg2XYmcX1");
http.addHeader("token", "1234");
```
then replacing went wrong. This is fixed with this PR.
* Fix persistance issue found, see ESP8266 issue #6152
* Correcting the parsing of the header for HTTP1.0
* Send 'Connection: Close' header in case of HTTP1.0
* Let reuse connection depend on protocol used: HTTP1.0 or HTTP1.1
* Fixed reuse, added null ptr checks, added check for _trainsportTraits in connect() in case _client was set null
* Fix reuse connection issues, similar to ESP8266 PR #6176
* Pass client parameter into two new begin() functions. Set other begin() functions deprecated. Updated library version to 1.2
* Added working HTTPS example on a public url with a certificate
* Remove two unnecessary tests in ::disconnect()
* Add a scoping block to BasicHttpsClient.ino to assure HTTPClient is destroyed before WiFiClientSecure
* Added check to handle mixup of old and present api properly
* Correct HTTPClient::setTimeout() to convert milliseconds to seconds. Correct WiFiClient::setTimeout() to call Stream::setTimeout() with seconds converted back to milliseconds. Remove inproper checks for _insecure.
* Added small comment because it looked like the Travis build did not finish
* Fix possible infinite loop in the example
* Remove workaround of sockets always return -76
Remove workaround of sockets always return -76 (because it's fixed on IDF now)
Remove delay during handshake (improving stability)
* Remove unusable mbedtls_net of context creation
* Fix bad destructor
* Compatibility with WiFiClient for HTTPClient
* Initial port from ESP8266
Changed SHA1 fingerprint by Root CA verification
Changed log system
* Remove deprecated function
