Feat: Support for Microsoft Oauth in Email Channel (#6227)

- Adds the backend APIs required for Microsoft Email Channels

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>
Co-authored-by: Sojan <sojan@pepalo.com>

app/services/microsoft/refresh_oauth_token_service.rb

@@ -0,0 +1,53 @@
+# refer: https://gitlab.com/gitlab-org/ruby/gems/gitlab-mail_room/-/blob/master/lib/mail_room/microsoft_graph/connection.rb
+# refer: https://github.com/microsoftgraph/msgraph-sample-rubyrailsapp/tree/b4a6869fe4a438cde42b161196484a929f1bee46
+# https://learn.microsoft.com/en-us/azure/active-directory/develop/active-directory-configurable-token-lifetimes
+class Microsoft::RefreshOauthTokenService
+  pattr_initialize [:channel!]
+
+  # if the token is not expired yet then skip the refresh token step
+  def access_token
+    provider_config = channel.provider_config.with_indifferent_access
+    if Time.current.utc >= expires_on(provider_config['expires_on'])
+      # Token expired, refresh
+      new_hash = refresh_tokens
+      new_hash[:access_token]
+    else
+      provider_config[:access_token]
+    end
+  end
+
+  def expires_on(expiry)
+    # we will give it a 5 minute gap for safety
+    expiry.presence ? DateTime.parse(expiry) - 5.minutes : Time.current.utc
+  end
+
+  # <RefreshTokensSnippet>
+  def refresh_tokens
+    token_hash = channel.provider_config.with_indifferent_access
+    oauth_strategy = ::MicrosoftGraphAuth.new(
+      nil, ENV.fetch('AZURE_APP_ID', nil), ENV.fetch('AZURE_APP_SECRET', nil)
+    )
+
+    token_service = OAuth2::AccessToken.new(
+      oauth_strategy.client, token_hash['access_token'],
+      refresh_token: token_hash['refresh_token']
+    )
+
+    # Refresh the tokens
+    new_tokens = token_service.refresh!.to_hash.slice(:access_token, :refresh_token, :expires_at)
+
+    update_channel_provider_config(new_tokens)
+    channel.provider_config
+  end
+  # </RefreshTokensSnippet>
+
+  def update_channel_provider_config(new_tokens)
+    new_tokens = new_tokens.with_indifferent_access
+    channel.provider_config = {
+      access_token: new_tokens[:access_token],
+      refresh_token: new_tokens[:refresh_token],
+      expires_on: Time.at(new_tokens[:expires_at]).utc.to_s
+    }
+    channel.save!
+  end
+end