This commit is a significant rewriting of client-side discuss, chatter,
chat window, and messaging menu using OWL. The behavior should be broadly
the same, with some slight functional changes here and there.

From a technical standpoint, the code of messaging is mainly organized in 2
main groups of modules:

- models, which are logical entities that depict the client-side state of
  messaging as a whole.
- components, which are in charge of displaying information from models.

This refactoring also introduces new JS guidelines regarding folder structure
(/static) and naming rules for JS modules.

Community PR: https://github.com/odoo/odoo/pull/39023
Enterprise PR: https://github.com/odoo/enterprise/pull/6249

Task-1914207

This PR is a collaborative work by Alexandre, Julien, Sébastien and Xavier,
with the precious help of Lucas to speed it up towards the end.

closes odoo/odoo#39023

Related: odoo/enterprise#6249
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>
Co-authored-by: Alexandre Kühn <aku@odoo.com>
Co-authored-by: Julien Giannone <jgi@odoo.com>
Co-authored-by: Lucas Perais <lpe@odoo.com>
Co-authored-by: Sébastien Theys <seb@odoo.com>
Co-authored-by: Xavier Dubuc <xdu@odoo.com>

This commit fixes the document viewer: the document viewer
was altering the `type` key of attachment objects, this issue was causing
matching errors in some cases.

With this commit, the document viewer widget uses its own key `attachment.fileType`
to store the information that used to override `attachment.type`

closes odoo/odoo#32414

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

Following the changes to the document viewer to make it more flexible
for use in documents (89f20d2c297d99d4eb0ded8be78fbf86b8ec45d3), the download route wasn't changed accordingly.

This commit fixes this issue so the download route is based on
the model of the viewer.

closes odoo/odoo#32207

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

Part of task 1896658

Co-authored-by: Aaron Bohy <aab@odoo.com>
Co-authored-by: Christophe Matthieu <chm@odoo.com>
Co-authored-by: Mathieu Duckerts-Antoine <dam@odoo.com>
Co-authored-by: David Monjoie <dmo@odoo.com>
Co-authored-by: Martin Geubelle <mge@odoo.com>
Co-authored-by: svs-odoo <svs@odoo.com>
Co-authored-by: Vincent Schippefilt <vsc@odoo.com>

Moved the field 'active', 'res_model_name' and 'thumbnail' from
ir.attachment to enterprise's documents.document.

Moved the pdf split feature to enterprise's Documents module.

task: #1908896

    -removed force_ext from ir.http.
    -added signature arg to web/image to differentiate cache entries by URL.
    -added an embed youtube viewer for youtube URL's
    -added a PDF splitter to the PDF viewer UI
    -added tests for mail's Document Viewer
    -added a "signature" param to web/image to go around the browser cache

    -thumbnail field of ir.attachment is now stored in the filestore
    as a distinct attachment.

task 1853490

Co-authored-by: Pierre Paridans <app@odoo.com>

This commit is the counter-part of an enteprise commit introducing
the Documents app.

Here is a summary of what has been done:
  - tweak unlink of ir_attachment to prevent unlink recursivity
    (when attachments are attached to ir_attachments)
  - improve ir_attachment kanban view
  - add several arguments to binary_content controller:
    - 'force_ext': to force the extension in the filename, base on
      mimetype
    - 'share_token' and 'share_id': to autorize download from a
      share link
  - add 'thumbnail' field on ir_attachment to optimize Kanban view
  - add 'upper_limit' argument to image to allow to bypass the
    500*500 size limit
  - DocumentViewer now handles text files

More information available on task 1853490

Co-authored-by: Pierre Paridans <app@odoo.com>
Co-authored-by: sri-odoo <sri@odoo.com>
Co-authored-by: ThanhDodeurOdoo <tso@odoo.com>