Capitalize TwiML tags; ignore slim-lint offense

**Why**: TwiML tags are case-sensitive according to Twilio
documentation, so we need to ignore the `TagCase` slim-lint offense
for `app/views/voice/otp/show.xml.slim`. For some reason, using the
exclude option under `TagCase` doesn't work, so I had to ignore the
file globally.

.slim-lint.yml

@@ -1,6 +1,11 @@
 exclude:
     - 'app/views/shared/_flashes.html.slim'
     - 'app/views/shared/_null.html.slim'
+    # The file below is ignored globally because for some reason,
+    # excluding it under the `TagCase` section below doesn't work.
+    # We need to exclude this file because slim-lint wants all XML
+    # tags to be lowercase, but Twilio requires them to be uppercase.
+    - 'app/views/voice/otp/show.xml.slim'
 linters:
   LineLength:
     max: 100
@@ -9,6 +14,6 @@ linters:
       - 'app/views/pages/privacy_policy.html.slim'
   TagCase:
     exclude:
-     - 'app/views/voice/otp/show.xml.slim'
+      - 'app/views/voice/otp/show.xml.slim'
   RuboCop:
     enabled: true

app/views/voice/otp/show.xml.slim

@@ -1,9 +1,9 @@
 doctype xml
 response
-  say language="#{I18n.locale}"
+  Say language="#{I18n.locale}"
     = @message
   - if @action_url
-    gather numDigits="1" action=@action_url
-      say language="#{I18n.locale}"
+    Gather numDigits="1" action=@action_url
+      Say language="#{I18n.locale}"
         = t('voice.otp.repeat_instructions')
-  hangup /
+  Hangup /

spec/controllers/voice/otp_controller_spec.rb

@@ -28,19 +28,19 @@
       let(:code) { '1234' }
       let(:encrypted_code) { cipher.encrypt(code) }
 
-      it 'tells Twilio to <say> the code with pauses in between' do
+      it 'tells Twilio to <Say> the code with pauses in between' do
         action
 
         doc = Nokogiri::XML(response.body)
-        say = doc.css('say').first
+        say = doc.css('Say').first
         expect(say.text).to include('1, 2, 3, 4,')
       end
 
       it 'sets the lang attribute to english' do
         action
 
         doc = Nokogiri::XML(response.body)
-        say = doc.css('say').first
+        say = doc.css('Say').first
 
         expect(say[:language]).to eq('en')
       end
@@ -52,16 +52,16 @@
           action
 
           doc = Nokogiri::XML(response.body)
-          say = doc.css('say').first
+          say = doc.css('Say').first
 
           expect(say[:language]).to eq('es')
         end
 
-        it 'passes locale into the <gather> action URL' do
+        it 'passes locale into the <Gather> action URL' do
           action
 
           doc = Nokogiri::XML(response.body)
-          gather = doc.css('gather').first
+          gather = doc.css('Gather').first
 
           params = URIService.params(gather[:action])
           expect(params[:locale]).to eq('es')
@@ -75,36 +75,36 @@
           action
 
           doc = Nokogiri::XML(response.body)
-          say = doc.css('say').first
+          say = doc.css('Say').first
 
           expect(say[:language]).to eq('fr')
         end
 
-        it 'passes locale into the <gather> action URL' do
+        it 'passes locale into the <Gather> action URL' do
           action
 
           doc = Nokogiri::XML(response.body)
-          gather = doc.css('gather').first
+          gather = doc.css('Gather').first
 
           params = URIService.params(gather[:action])
           expect(params[:locale]).to eq('fr')
         end
       end
 
-      it 'has a <gather> with instructions to repeat with a repeat_count' do
+      it 'has a <Gather> with instructions to repeat with a repeat_count' do
         action
 
         doc = Nokogiri::XML(response.body)
-        gather = doc.css('gather').first
+        gather = doc.css('Gather').first
 
         expect(gather[:action]).to include('repeat_count=4')
       end
 
-      it 'puts the encrypted code in the <gather> action' do
+      it 'puts the encrypted code in the <Gather> action' do
         action
 
         doc = Nokogiri::XML(response.body)
-        gather = doc.css('gather').first
+        gather = doc.css('Gather').first
         params = URIService.params(gather[:action])
 
         expect(cipher.decrypt(params[:encrypted_code])).to eq(code)
@@ -113,11 +113,11 @@
       context 'when repeat_count counts down to 1' do
         let(:repeat_count) { 1 }
 
-        it 'does not have a <gather> in the response' do
+        it 'does not have a <Gather> in the response' do
           action
 
           doc = Nokogiri::XML(response.body)
-          expect(doc.css('gather')).to be_empty
+          expect(doc.css('Gather')).to be_empty
         end
       end
     end