Allow activation of Jira Import

In order to import issues from a JIRA Project we need an object that will store the name of the project and the current state of the import job.

• Object should record the JIRA project name from which issues will be imported;
• Object should have an enum to record the state of the import (started/in progress/finished);
• Object should belong_to a single GitLab project;
• A GitLab project may have more than one of these objects (see Questions#1);
• It should be possible to create this object via the internal API using the JIRA project name;

Questions to answer in planning

1. Is it required to support multiple JIRA projects for one GitLab project
2. Is it possible/desirable to reuse project_import_state.rb

Screenshots

If we re-use the current project settings page for collecting JIRA credentials, we'll need a button & form in the interface to collect JIRA project information and commence the import.

Step 1 - Issue List

Step 2 - Select Jira From Dropdown

Step 3a - Go To Jira Import Page -- If Integration Not Active

Step 3a.1 - Go To Integration Settings

Upon user successfully activating the Jira integration, redirect back to the import page

Step 3b - If Integration Active

If the integration is active, the user will then be taken to the project selection screen to choose which Jira project to import from.

Feature flag

jira_issue_import