[REF][MOV] documentation apocalypse

Prior to this commit, the Odoo documentation was mainly split between
two repositories: odoo/odoo/doc and odoo/documentation-user. Some bits
of documentation were also hosted elsewhere (e.g., wiki, upgrade, ...).
This was causing several problems among which:
  - The theme, config, Makefile, and similar technical resources had to
    be duplicated. This resulted in inconsistent layout, features, and
    build environments from one documentation to another.
  - Some pages did not fit either documentation as they were relevant
    for both users and developers. Some were relevant to neither of the
    two (e.g., DB management).
  - Cross-doc references had to be absolute links and they broke often.
  - Merging large image files in the developer documentation would bloat
    the odoo/odoo repository. Some contributions had to be lightened to
    avoid merging too many images (e.g., Odoo development tutorials).
  - Long-time contributors to the user documentation were chilly about
    going through the merging process of the developer documentation
    because of the runbot, mergebot, `odoo-dev` repository, etc.
  - Some contributors would look for the developer documentation in the
    `odoo/documentation-user` repository.
  - Community issues about the user documentation were submitted on the
    `odoo/odoo` repository and vice-versa.

Merging all documentations in one repository will allow us to have one
place, one theme, one work process, and one set of tools (build
environment, ...) for all of the Odoo docs.

As this is a good opportunity to revamp the layout of the documentation,
a brand new theme replaces the old one. It features a new way to
navigate the documentation, centered on the idea of always letting the
reader know what is the context (enclosing section, child pages, page
structure ...) of the page they are reading. The previous theme would
quickly confuse readers as they navigated the documentation and followed
cross-application links.

The chance is also taken to get rid of all the technical dangling parts,
performance issues, and left-overs. Except for some page-specific JS
scripts, the Odoo theme Sphinx extension is re-written from scratch
based on the latest Sphinx release to benefit from the improvements and
ease future contributions.

task-2351938
task-2352371
task-2205684
task-2352544

Closes #945

content/applications/websites/website/publish/domain_name.rst

@@ -0,0 +1,105 @@
+=============================
+How to use my own domain name
+=============================
+
+By default, your Odoo Online instance and website have a *.odoo.com* domain name, 
+for both the URL and the emails. 
+But you can change to a custom one (e.g. www.yourcompany.com).
+
+What is a good domain name
+==========================
+Your website address is as important to your branding as the name of your 
+business or organization, so put some thought into changing it for a proper 
+domain. Here are some tips:
+
+- Simple and obvious
+- Easy to remember and spell
+- The shorter the better
+- Avoid special characters
+- Aim for a .com and/or your country extension
+
+Read more: `How to Choose a Domain Name for Maximum SEO <https://www.searchenginejournal.com/choose-a-domain-name-maximum-seo/158951/>`__
+
+How to buy a domain name
+========================
+Buy your domain name at a popular registrar:
+
+- `GoDaddy <https://www.godaddy.com>`__  
+- `Namecheap <https://www.namecheap.com>`__  
+- `OVH <https://www.ovh.com>`__ 
+
+.. note:: Steps to buy a domain name are pretty much straight forward. 
+   In case of issue, check out those easy tutorials:
+
+   - `GoDaddy <https://roadtoblogging.com/buy-domain-name-from-godaddy>`__
+   - `Namecheap <https://www.loudtips.com/buy-domain-name-hosting-namecheap//>`__
+
+   Feel free to buy an email server to have email addresses using your domain name.
+   However don't buy any extra service to create or host your website. 
+   This is Odoo's job!
+
+.. _custom_domain:
+
+
+How to apply my domain name to my Odoo instance
+===============================================
+First let's authorize the redirection (yourcompany.com -> yourcompany.odoo.com):
+
+* Open your Odoo.com account from your homepage.
+
+.. image:: media/domain_name01.png
+    :align: center
+
+* Go to the *Manage Databases* page.
+
+.. image:: media/domain_name02.png
+    :align: center
+
+* Click on *Domains* to the right of the database you would like to redirect.
+
+.. image:: media/domain_name03.png
+    :align: center
+
+* A database domain prompt will appear. Enter your custom domain 
+  (e.g. www.yourcompany.com).
+
+
+.. image:: media/domain_name04.png
+    :align: center
+
+We can now apply the redirection from your domain name's manager account:
+
+* Log in to your account and search for the DNS Zones management page.
+
+* Create a CNAME record *www.yourdomain.com* pointing to *mywebsite.odoo.com*.
+  If you want to use the naked domain (e.g. yourdomain.com), you need to redirect 
+  *yourdomain.com* to *www.yourdomain.com*.
+
+.. note:: Here are some specific guidelines to create a CNAME record:
+
+   - `GoDaddy <https://be.godaddy.com/fr/help/add-a-cname-record-19236>`__
+   - `Namecheap <https://www.namecheap.com/support/knowledgebase/article.aspx/9646/10/how-can-i-set-up-a-cname-record-for-my-domain>`__
+   - `OVH <https://www.ovh.co.uk/g1519.exchange_20132016_how_to_add_a_cname_record>`__
+
+How to enable SSL (HTTPS) for my Odoo instance
+==============================================
+
+Until recently, Odoo users needed to use a third-party CDN service provider such as CloudFlare to enable SSL.
+
+It is not required anymore: Odoo generates the certificate for you automatically, using integration with `Let's Encrypt Certificate Authority and ACME protocol <https://letsencrypt.org/how-it-works/>`__.
+In order to get this, simply add your domain name in your customer portal (a separate certificate is generated for each domain name specified).
+
+.. warning::
+  **Please note that the certificate generation may take up to 24h.**
+
+If you already use CloudFlare or a similar service, you can keep using it or simply change for Odoo. The choice is yours.
+
+My website is indexed twice by Google
+=====================================
+
+If you set up a custom domain *mydomain.com* name for *mydatabase.odoo.com*,
+Google indexes your website under both names. This is a limitation of the Odoo cloud platforms/
+
+.. seealso::
+
+  * :doc:`../../../productivity/discuss/email_servers`