pyinvoice: actually expose the "templated_text()" function to templat…

…es and extend the documentation accordingly

README.md

@@ -33,6 +33,24 @@ will be rendered as a currency value.
 </item>
 ```
 
+To apply templating you need to call the `tt()` template function in your html template, for example like this:
+
+```html
+{% for item in invoice.get_invoice_items() %}
+<tr class="position-row">
+    <td>
+        {% if item.get_title() %}
+        <div class="pos-title">{{ tt(item.get_title(), item) }}</div>
+        {% endif %}
+        {{ tt(item.get_subtext(), item) }}
+    </td>
+    <td class="net-amount">
+        {{ f.amount(item.get_price(net=True)) }}
+    </td>
+</tr>
+{% endfor %}
+```
+
 If the invoice is set to English/USD the rendered string will be "My work: 16.75 h at $60.00".
 For German/EUR the output is "My work: 16,75 h at 60,00 €".
 

src/schwarz/pyinvoice/pdf_generator.py

@@ -7,6 +7,8 @@
 from babel.support import Format, Translations
 import jinja2
 
+from .templating import templated_text
+
 
 __all__ = ['generate_pdf', 'is_weasyprint_available']
 
@@ -27,7 +29,12 @@ def generate_pdf(invoice, invoice_cfg, target_path, *, with_logo=False):
     template_dir = template_path.parent
     template = load_invoice_template(template_path, locale=invoice.language)
     _format = build_formatter(invoice.language, currency=invoice.currency)
-    template_params = {'f': _format, **invoice_cfg, 'with_logo': with_logo}
+    template_params = {
+        'tt': lambda text, dbobj: templated_text(text, dbobj, _format),
+        'f': _format,
+        **invoice_cfg,
+        'with_logo': with_logo,
+    }
 
     html_str = template.render(invoice=invoice, **template_params)
     with store_generated_html(template_dir, html_str) as path_html: