Jira Cloud - Can I add dynamic content to Jira issues?

We are using Jira Cloud for the onboarding process of new employees. It would be nice if we could add dynamic content when Jira issues are created. For example, the name of the new employee should be added to the summary, the first work day should be added and so on.

Are there any apps which cover this kind of process?

There is an app which lets you add dynamic content based on custom variables to Jira issues.
With Easy Issue & Subtask Templates you can create templates for issues (even with epics and subtasks) and add variables.

You can create variables based on different field types (e.g. text, user picker, date, select, multi-select). Add variables to your Jira issue fields (e.g. summary, assignee, etc.) so users have to fill them out when using a template. The related information will be added to the jira issues, based on your configuration.

For more information please visit the documentation.