Make Bitbucket Cloud superseded pull requests as closed

The Bitbucket pull request API
(https://developer.atlassian.com/bitbucket/api/2/reference/) reports
four different states for pull requests:

1. MERGED
2. SUPERSEDED
3. OPEN
4. DECLINED

Previously, we were not handling the SUPERSEDED case. This commit now
changes SUPERSEDED pull requests as closed.

Possible fix for https://gitlab.com/gitlab-org/gitlab/issues/34656

changelogs/unreleased/sh-bitbucket-importer-handle-superseded.yml

+---
+title: Make Bitbucket Cloud superseded pull requests as closed
+merge_request: 19193
+author:
+type: fixed

lib/bitbucket/representation/pull_request.rb

@@ -16,9 +16,10 @@ module Bitbucket
       end
 
       def state
-        if raw['state'] == 'MERGED'
+        case raw['state']
+        when 'MERGED'
           'merged'
-        elsif raw['state'] == 'DECLINED'
+        when 'DECLINED', 'SUPERSEDED'
           'closed'
         else
           'opened'

spec/lib/bitbucket/representation/pull_request_spec.rb

@@ -20,6 +20,7 @@ describe Bitbucket::Representation::PullRequest do
   describe '#state' do
     it { expect(described_class.new({ 'state' => 'MERGED' }).state).to eq('merged') }
     it { expect(described_class.new({ 'state' => 'DECLINED' }).state).to eq('closed') }
+    it { expect(described_class.new({ 'state' => 'SUPERSEDED' }).state).to eq('closed') }
     it { expect(described_class.new({}).state).to eq('opened') }
   end