Fix JIRA not working when a trailing slash is included

Leaving a trailing slash in the context option causes the jira-ruby
gem to add an extra slash in HTTP requests to the URL, preventing
JIRA from working properly.

Closes #42494

app/models/project_services/jira_service.rb

@@ -43,7 +43,7 @@ class JiraService < IssueTrackerService
       username: self.username,
       password: self.password,
       site: URI.join(url, '/').to_s,
-      context_path: url.path,
+      context_path: url.path.chomp('/'),
       auth_type: :basic,
       read_timeout: 120,
       use_cookies: true,

changelogs/unreleased/sh-fix-jira-trailing-slash.yml

@@ -0,0 +1,5 @@
+---
+title: Fix JIRA not working when a trailing slash is included
+merge_request:
+author:
+type: fixed

spec/models/project_services/jira_service_spec.rb

@@ -3,6 +3,29 @@ require 'spec_helper'
 describe JiraService do
   include Gitlab::Routing
 
+  describe '#options' do
+    let(:service) do
+      described_class.new(
+        project: build_stubbed(:project),
+        active: true,
+        username: 'username',
+        password: 'test',
+        jira_issue_transition_id: 24,
+        url: 'http://jira.test.com/path/'
+      )
+    end
+
+    it 'sets the URL properly' do
+      # jira-ruby gem parses the URI and handles trailing slashes
+      # fine: https://github.com/sumoheavy/jira-ruby/blob/v1.4.1/lib/jira/http_client.rb#L59
+      expect(service.options[:site]).to eq('http://jira.test.com/')
+    end
+
+    it 'leaves out trailing slashes in context' do
+      expect(service.options[:context_path]).to eq('/path')
+    end
+  end
+
   describe "Associations" do
     it { is_expected.to belong_to :project }
     it { is_expected.to have_one :service_hook }