The unit test in `test_base_document_layout` does not pass with
version 7.0.0 of PIL, which is loaded by default on Ubuntu 20.04.
The reason is that the color obtained from the image is slightly
different.  This fix slightly relaxes the test (in fact we don't care
about the exact color obtained in this test, we just want to make sure
that it doesn't crash)

opw-2342394 (original ticket)

closes odoo/odoo#59912

X-original-commit: 3028c814d62309bfa2a55f9aaa775738263d8326
Signed-off-by: Thomas Dieuzeide <tdi-odoo@users.noreply.github.com>

Behavior before the fix:

Uploading a grayscale image with transparency in the company logo field
of the document layout causes a crash:

```
  File "/data/build/odoo/addons/web/models/base_document_layout.py", line 89, in _compute_logo_colors
    wizard.logo_primary_color, wizard.logo_secondary_color = wizard_for_image._parse_logo_colors()
  File "/data/build/odoo/addons/web/models/base_document_layout.py", line 191, in _parse_logo_colors
    color[1][2] > white_threshold) and color[1][3] > 0:
Exception

...
IndexError: tuple index out of range
```

To reproduce, use the `logo_ci.png` image included in the unit test
data and load it in the document layout (under General Settings).

The system does not detect that the image does not have color
information and attempts to read the R,G,B values (but the image only
has 2 values per pixel: the grayscale value and the alpha)

Versions affected: 13, 14

Behavior after the fix:

The image is loaded correctly (arguably, there is not a lot of interest
in detecting the primary color of a grayscale image, but the script
still returns a (gray) value which is preferrable to a traceback)

opw-2352394

closes odoo/odoo#59381

X-original-commit: 9efe5608aa4fb4f66475d3cb3e15ea332a3ded38
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

The document layout preview is a complete defferent simplified template
with its own css that replicates at best the different styles.
It does not have the external layout features and lack of fidelity.

The new preview actually use the real documents templates and put the
result in an iframe. It now has a high fidelity, though not perfect.

The goal is for a better onboarding, where clients see easely how
documents will look if they had an app to generate them. Of course, the
data on the document is a false invoice.

Refactor all this from base to web.

Task ID 2304177

closes odoo/odoo#56415

Signed-off-by: Lucas Perais (lpe) <lpe@odoo.com>