feat: add Jira issue fetcher component and pipeline

[mathislucka]

Overview

This PR adds support for fetching issues from Jira to complement the existing GitHub issue fetcher functionality. It creates a similar Haystack component structure that integrates with Jira's REST API to fetch issue data and convert it to chat messages for the agent.

Features Added

1. JiraIssueViewer Component: Fetches Jira issues and comments, handling Jira's Atlassian Document Format (ADF) content structure
2. FetchJiraIssue SuperComponent: Combines issue fetching, document conversion, and branch creation like the GitHub counterpart
3. Jira Agent Pipeline: Parallels the GitHub agent pipeline but uses the Jira components

Implementation Details

Jira API Integration

• Implemented authentication using Jira API token and email
• Added support for parsing Jira Cloud URLs (e.g., https://your-domain.atlassian.net/browse/PROJECT-123)
• Created helper methods to extract readable text from Jira's complex document format (ADF)

Component Structure

• Created components with the same interfaces as their GitHub counterparts for consistency
• Maintained the same document/message conversion process for seamless integration

Pipeline Configuration

• Added a Jira agent pipeline that mirrors the GitHub agent pipeline
• Updated pipelines package exports to include both agent types
• Reused the system prompt from the GitHub agent since the agent behavior is identical

Tests

• Added comprehensive unit tests for the new components
• Included mocking of Jira API responses for testing

Testing Considerations

The implementation has been tested with unit tests that verify:

• Correct parsing of Jira URLs
• Proper extraction of text from Jira's document format
• Error handling for API issues
• Component integration and serialization

Manual testing should verify:

1. Authentication with real Jira credentials
2. Fetching real issues from Jira instances
3. End-to-end pipeline execution

Environment Requirements

To use this feature, users will need to set the following environment variables:

• JIRA_API_TOKEN: A valid Jira API token
• JIRA_EMAIL: The email associated with the Jira account

Closes #19