Update ExternalIssue regex for JIRA integration

The pattern in the `::reference_pattern` class method in the
ExternalIssue model does not match all valid forms of JIRA project
names. I have updated the regex to match JIRA project names with numbers
and underscores. More information on valid JIRA project names can be
found here:
https://confluence.atlassian.com/jira/changing-the-project-key-format-192534.html

* The first character must be a letter,
* All letters used in the project key must be from the Modern Roman Alphabet and upper case, and
* Only letters, numbers or the underscore character can be used.

1 files changed, 15 insertions, 0 deletions

diff --git a/spec/models/external_issue_spec.rb b/spec/models/external_issue_spec.rb
index 6ec6b9037a4..9b144dd1ecc 100644
--- a/spec/models/external_issue_spec.rb
+++ b/spec/models/external_issue_spec.rb
@@ -10,6 +10,21 @@ describe ExternalIssue, models: true do
     it { is_expected.to include_module(Referable) }
   end
 
+  describe '.reference_pattern' do
+    it 'allows underscores in the project name' do
+      expect(ExternalIssue.reference_pattern.match('EXT_EXT-1234')[0]).to eq 'EXT_EXT-1234'
+    end
+
+    it 'allows numbers in the project name' do
+      expect(ExternalIssue.reference_pattern.match('EXT3_EXT-1234')[0]).to eq 'EXT3_EXT-1234'
+    end
+
+    it 'requires the project name to begin with A-Z' do
+      expect(ExternalIssue.reference_pattern.match('3EXT_EXT-1234')).to eq nil
+      expect(ExternalIssue.reference_pattern.match('EXT_EXT-1234')[0]).to eq 'EXT_EXT-1234'
+    end
+  end
+
   describe '#to_reference' do
     it 'returns a String reference to the object' do
       expect(issue.to_reference).to eq issue.id