Chinese garbled of alarm message

[unhappydepig]

• Why do you submit this issue?
• Bug

---

Bug

• Which version of SkyWalking, OS and JRE?
  SkyWalking6.1.0
• Which company or project?
  zdp
• What happen?
  I configure Chinese warning message in alarmRule, But the message I received on the server is garbled.
  
  By looking at the source code[org.apache.skywalking.oap.server.core.alarm.provider.WebhookCallback ], I learned that we used StringEntity to transfer information, but did not specify the encoding.
  

[wu-sheng]

All SkyWalking codes and settings are in UTF-8 by default. So we don't set those explicitly. Which encoding are .you using at server side?

[unhappydepig]

The charset for my server is UTF-8 and runs the test case. When I manually specify the encoding format as UTF-8. The server can respond normally.

At the same time I noticed. If no charset is specified, the default encoding format of “StringEntity” is “HTTP.DEF_CONTENT_CHARSET” and the variable defaults to “ISO-8859-1”

[wu-sheng]

We are open to accepting your pull request, please submit you.

[wu-sheng]

@unhappydepig, Will you submit a pull request to fix this?