[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>

docs/examples/jinja_templating.md

@@ -0,0 +1,133 @@
+# Enhanced Templating with Jinja2
+
+CrewAI now supports enhanced templating using Jinja2, while maintaining compatibility with the existing templating system.
+
+## Basic Usage
+
+The basic templating syntax remains the same:
+
+```python
+from crewai import Agent, Task, Crew
+
+# Define inputs
+inputs = {
+    "topic": "Artificial Intelligence",
+    "year": 2024,
+    "count": 5
+}
+
+# Create an agent with template variables
+researcher = Agent(
+    role="{topic} Researcher",
+    goal="Research the latest developments in {topic} for {year}",
+    backstory="You're an expert in {topic} with years of experience"
+)
+
+# Create a task with template variables
+research_task = Task(
+    description="Research {topic} and provide {count} key insights",
+    expected_output="A list of {count} key insights about {topic} in {year}",
+    agent=researcher
+)
+
+# Create a crew and pass inputs
+crew = Crew(
+    agents=[researcher],
+    tasks=[research_task],
+    inputs=inputs
+)
+
+# Run the crew
+result = crew.kickoff()
+```
+
+## Advanced Features
+
+The new templating system adds support for container types, object attributes, conditional statements, loops, and filters:
+
+### Container Types
+
+```python
+inputs = {
+    "topics": ["AI", "Machine Learning", "Data Science"],
+    "details": {"main_theme": "Technology Trends", "subtopics": ["Ethics", "Applications"]}
+}
+
+# Access list items
+task = Task(
+    description="Research {{topics[0]}} and {{topics[1]}}",
+    expected_output="Analysis of the topics"
+)
+
+# Access dictionary items
+task = Task(
+    description="Research {{details.main_theme}} with focus on {{details.subtopics[0]}}",
+    expected_output="Detailed analysis"
+)
+```
+
+### Conditional Statements
+
+```python
+inputs = {
+    "topic": "AI",
+    "priority": "high",
+    "deadline": "2024-12-31"
+}
+
+task = Task(
+    description="{% if priority == 'high' %}URGENT: {% endif %}Research {topic}{% if deadline %} by {{deadline}}{% endif %}",
+    expected_output="A report on {topic}"
+)
+```
+
+### Loop Statements
+
+```python
+inputs = {
+    "topics": ["AI", "Machine Learning", "Data Science"]
+}
+
+task = Task(
+    description="Research the following topics: {% for topic in topics %}{{topic}}{% if not loop.last %}, {% endif %}{% endfor %}",
+    expected_output="A report covering multiple topics"
+)
+```
+
+### Filters
+
+```python
+from datetime import datetime
+
+inputs = {
+    "topic": "AI",
+    "date": datetime.now()
+}
+
+task = Task(
+    description="Research {topic} as of {{date|date('%Y-%m-%d')}}",
+    expected_output="A report on {topic}"
+)
+```
+
+### Custom Objects
+
+```python
+from pydantic import BaseModel
+
+class Person(BaseModel):
+    name: str
+    age: int
+    
+    def __str__(self):
+        return f"{self.name} ({self.age})"
+
+inputs = {
+    "author": Person(name="John Doe", age=35)
+}
+
+task = Task(
+    description="Write a report authored by {author}",
+    expected_output="A report by {{author.name}}"
+)
+```