- Introduced a button to dynamically set the expression in the substitution line.
- The feature is available for converters of type "Odoo template", "Odoo template + Evaluation", and "Field".
- Added functionality to visualize how to define each converter, displaying a placeholder (example) for each converter type.
- The code has been designed to ease the integration of additional converters in the future.
- Refactored the code to improve performance and stability.

- Add missing python-magic requirement for package

- Added `ormcache` to improve performance by caching template retrieval
in `_get_cached_template`.
- Refactored template processing logic:
  - Introduced `_to_odoo_template` to centralize transformation
    of external templates into Odoo-compatible format.
  - Simplified template computation in `_compute_template` and
    `_compute_template_data` using cached templates.
- Removed redundant methods (`to_cache`) and consolidated logic for clarity.

- the file is correctly computed when fetched from redner
- the file name is standardized.

fixes the display of the button being quirky
also fix the button vanish when value==False

with barebone view management

& latest xcg/templates/odoo_module.

Similar in the 13.0 branch: 7cc12fb73390

converter backport in 2021-06.
In particular, add "HTML + mustache" / "MJML + mustache" instead of just "mustache".

Rework on relations converters
Remove deprecated field (ie: deserialize)
Use converter on mail template model
Updated the french translations

Added a custom converter image

Only required for mustache/handlebars template engines.

- Bump module version to 13.0.1.0.0
- Remove all the decorators @api.multi, @api.one and so on...
- Update translation files

Render HTML to PDF with weasyprint:

- Use substitution variables in ir.actions.report model
- Send paperformat field info to rednerd when generating a new report PDF
- Refactoring code

Add rednerd template management API to let the user save templates
for later use with the rendering api:

- POST: /api/v1/template/{account}
- PUT: /api/v1/template/{account}/{name}
- DELELTE: /api/v1/template/{account}/{name}

Render a custom template:

- POST: /api/v1/render