OOME Exception for CSV Export on large searches

Summary

This could be due to a large amount of worklog entries or comments etc.

This issue should look at how we can work with fields that can have an unbounded number of columns. This could be not allowing the export of worklog for example or thinking of an improvement to the way it is implemented to not cause this problem.

Steps to Reproduce

1. Get an instance with a large number of worklog entries/comments and issues
2. Go to search issues and do a search that will return a large number of issues with a lot of worklog entries. e.g. jql=
3. Click the export button
4. Click Export All Fields (CSV)

Expected Results

A CSV file should be produced.

Actual Results

An OOME exception is thrown.

Notes

(Optional - If Necessary)

Workaround

No workaround to get a csv file but can still export using the original HTML format.