[FIX] Added charset UTF-8 in requestBuilder

[svenmalvik]

We had an issue with sending a comment with special characters like the norwegian letter "ø" to stash. I added charset UTF-8 in requestBuilder.
Insight from Wikipedia about Json: JSON exchange in an open ecosystem must be encoded in UTF-8. (https://en.wikipedia.org/wiki/JSON)

[t-8ch]

Hi @svenmalvik, thanks for this!
Two points:

• Please squash the commits into one.
• Out of curiosity, how did the error manifest? Was there an exception, did it use the system encoding, or something else?

[svenmalvik]

I have squashed all commits into one.
I got an exception saying that it cannot post 0xf8 (norwegian letter ø) to stash. An upgrade of json_simple to 3.0.2 didn't fix the problem.

12:22:44 [INFO] {"errors":[{"context":null,"message":"Invalid UTF-8 start byte 0xf8\n at [Source: com.atlassian.stash.internal.web.util.web.CountingServletInputStream@41be8846; line: 1, column: 788]","exceptionName":"org.codehaus.jackson.JsonParseException"}]} 12:22:44 [ERROR] Unable to push SonarQube analysis overview to Stash 12:22:44 org.sonar.plugins.stash.exceptions.StashClientException: Unable to post a comment to vl-foreldrepenger #587. Received 400: org.codehaus.jackson.JsonParseException: Invalid UTF-8 start byte 0xf8 12:22:44 at [Source: com.atlassian.stash.internal.web.util.web.CountingServletInputStream@41be8846; line: 1, column: 788] 12:22:44 at org.sonar.plugins.stash.client.StashClient.validateResponse(StashClient.java:383)

[svenmalvik]

Done

[t-8ch]

Thanks!