feat: added grafana dashboards

[irfanuddinahmad]

This pull request enhances the extraction and conversion of Taiga user stories by standardizing date handling, improving status mapping, and enriching the domain model with additional fields. The changes improve data consistency and enable more detailed analytics, such as lead time calculation and better assignee/milestone information.

User story extraction improvements:

• Changed created_date, modified_date, and finish_date fields in the extractor to use time.Time pointers for accurate time handling, and added extraction of is_closed, assigned_to_extra_info.full_name_display, milestone_name, and blocked_note for richer user story data. [1] [2] [3]
• Updated the import statements to include the time package for time parsing.

User story conversion enhancements:

• Standardized the mapping of Taiga's is_closed field to DevLake's status (TODO/DONE), set IssueKey to use the reference number, and added new fields: CreatedDate, UpdatedDate, ResolutionDate, AssigneeId, and AssigneeName to the ticket.Issue model.
• Added calculation of lead time in minutes for closed user stories, based on the difference between creation and resolution dates.
• Imported the fmt package to support string formatting for new fields.