[FEATURE] Improve agent/task templating with Jinja2

Fixes #2650

- Add support for container types (List, Dict, Set)
- Add support for standard objects (datetime)
- Add support for custom objects
- Add support for conditional and loop statements
- Add support for filtering options
- Maintain backward compatibility with existing templates
- Add comprehensive tests
- Add documentation with examples

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/utilities/test_jinja_templating.py

@@ -0,0 +1,81 @@
+import pytest
+import datetime
+from pydantic import BaseModel
+from typing import List, Dict, Any
+from crewai.utilities.jinja_templating import to_jinja_template, render_template
+
+class Person(BaseModel):
+    name: str
+    age: int
+    
+    def __str__(self):
+        return f"{self.name} ({self.age})"
+
+class TestJinjaTemplating:
+    def test_to_jinja_template(self):
+        assert to_jinja_template("Hello {name}!") == "Hello {{name}}!"
+        
+        assert to_jinja_template("Hello {{name}}!") == "Hello {{name}}!"
+        
+        assert to_jinja_template("Hello {name} and {{title}}!") == "Hello {{name}} and {{title}}!"
+        
+        assert to_jinja_template("") == ""
+        
+        assert to_jinja_template("Hello world!") == "Hello world!"
+    
+    def test_render_template_simple_types(self):
+        inputs = {"name": "John", "age": 30, "active": True, "height": 1.85}
+        
+        assert render_template("Hello {name}!", inputs) == "Hello John!"
+        assert render_template("Age: {age}", inputs) == "Age: 30"
+        assert render_template("Active: {active}", inputs) == "Active: True"
+        assert render_template("Height: {height}", inputs) == "Height: 1.85"
+        
+        assert render_template("{name} is {age} years old", inputs) == "John is 30 years old"
+    
+    def test_render_template_container_types(self):
+        inputs = {
+            "items": ["apple", "banana", "orange"],
+            "person": {"name": "John", "age": 30}
+        }
+        
+        assert render_template("First item: {{items[0]}}", inputs) == "First item: apple"
+        
+        assert render_template("Person name: {{person.name}}", inputs) == "Person name: John"
+        
+        assert render_template(
+            "Items: {% for item in items %}{{item}}{% if not loop.last %}, {% endif %}{% endfor %}",
+            inputs
+        ) == "Items: apple, banana, orange"
+        
+        assert render_template(
+            "{% if items|length > 2 %}Many items{% else %}Few items{% endif %}",
+            inputs
+        ) == "Many items"
+    
+    def test_render_template_datetime(self):
+        today = datetime.datetime.now()
+        inputs = {"today": today}
+        
+        assert render_template("Today: {{today|date}}", inputs) == f"Today: {today.strftime('%Y-%m-%d')}"
+        
+        assert render_template("Today: {{today|date('%d/%m/%Y')}}", inputs) == f"Today: {today.strftime('%d/%m/%Y')}"
+    
+    def test_render_template_custom_objects(self):
+        person = Person(name="John", age=30)
+        inputs = {"person": person}
+        
+        assert render_template("Person: {person}", inputs) == "Person: John (30)"
+        
+        assert render_template("Person name: {{person.name}}", inputs) == "Person name: John"
+    
+    def test_render_template_error_handling(self):
+        inputs = {"name": "John"}
+        
+        with pytest.raises(KeyError) as excinfo:
+            render_template("Hello {age}!", inputs)
+        assert "Template variable 'age' not found" in str(excinfo.value)
+        
+        with pytest.raises(ValueError) as excinfo:
+            render_template("Hello {name}!", {})
+        assert "Inputs dictionary cannot be empty" in str(excinfo.value)