Fix epic_key column in list call. Closes #75

[karanpopat]

Example query results

Results

> select
  key,
  id, 
  epic_key,
  project_key
from
  jira_issue
where
  key in ('SBT-1', 'SBT-2', 'SBT-3')
+-------+-------+----------+-------------+
| key   | id    | epic_key | project_key |
+-------+-------+----------+-------------+
| SBT-3 | 10052 | SBT-1    | SBT         |
| SBT-1 | 10050 | <null>   | SBT         |
| SBT-2 | 10051 | SBT-1    | SBT         |
+-------+-------+----------+-------------+

Time: 396ms. Rows fetched: 1. Hydrate calls: 0.
> select
  key,
  id,
  epic_key,
  project_key
from
  jira_issue
where
  project_key = 'SBT'
+-------+-------+----------+-------------+
| key   | id    | epic_key | project_key |
+-------+-------+----------+-------------+
| SBT-3 | 10052 | SBT-1    | SBT         |
| SBT-1 | 10050 | <null>   | SBT         |
| SBT-2 | 10051 | SBT-1    | SBT         |
+-------+-------+----------+-------------+

Time: 0.9s. Rows fetched: 3. Hydrate calls: 3.

[misraved]

@karanpopat thanks for looking into this issue 👍. I have left a minor review comment.

Also, do the APIs for ListConfig and GetConfig return similar data for the epic_key column?

Could you please add different example queries in the PR body to justify that both APIs return similar values?

[karanpopat]

@misraved
Findings:

• The SDK is not returning the custom fields in the List call - epic_key is a part of the custom fields. Have raised an issue for the same - IssueFields.Unknowns and IssueFields.Names not returned in Issue.SearchWithContext api andygrunwald/go-jira#636
• The issue persists even after updating the SDK
• One workaround could be by using the get api as hydrate for the column. Which is of course an extra api call.
• Another would be to use the raw searchIssue endpoint to fetch the List call data, which returns some means to fetch the epic data.

Have modified the list call in this PR to use the rest/api/2/search endpoint.