Ensure JSON is used for Sentry requests

lib/sentry/client.rb

@@ -33,6 +33,7 @@ module Sentry
     def request_params
       {
         headers: {
+          'Content-Type' => 'application/json',
           'Authorization' => "Bearer #{@token}"
         },
         follow_redirects: false
@@ -47,7 +48,7 @@ module Sentry
 
     def http_put(url, params = {})
       http_request do
-        Gitlab::HTTP.put(url, **request_params.merge(body: params))
+        Gitlab::HTTP.put(url, **request_params.merge(body: params.to_json))
       end
     end
 

spec/lib/sentry/client/issue_spec.rb

@@ -30,7 +30,7 @@ describe Sentry::Client::Issue do
     let(:default_httparty_options) do
       {
         follow_redirects: false,
-        headers: { "Authorization" => "Bearer test-token" }
+        headers: { 'Content-Type' => 'application/json', 'Authorization' => "Bearer test-token" }
       }
     end