/usr/share/accounts/services/google-calendar.service is in evolution-data-server-online-accounts 3.10.4-0ubuntu1.6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | <?xml version="1.0" encoding="UTF-8"?>
<service id="google-calendar">
  <type>calendar</type>
  <name>Google Calendar</name>
  <provider>google</provider>
  <translations>evolution-data-server-3.10</translations>
  
  <template>
    <group name="auth">
      <setting name="method">oauth2</setting>
      <setting name="mechanism">web_server</setting>
      <group name="oauth2">
        <group name="web_server">
          <setting name="Host">accounts.google.com</setting>
          <setting name="TokenPath">o/oauth2/token</setting>
          <setting name="RedirectUri">https://live.gnome.org/Evolution</setting>
          <setting name="ClientId">796629365126.apps.googleusercontent.com</setting>
          <setting name="ClientSecret">3NbR94RM-DTnA81BWjiJe4TP</setting>
          <setting type="as" name="Scope">['https://www.googleapis.com/auth/userinfo.email','https://mail.google.com/','https://www.google.com/m8/feeds/','https://www.googleapis.com/auth/calendar']</setting>
        </group>
      </group>
    </group>
  </template>
</service>
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