Jira on-prem

[agregoryfs]

Is your feature request related to a problem?

We integrate with JIRA SaaS, but larger teams use the Jira on-prem and want us to integrate there.

Describe the solution you'd like.

Allow customers using self-hosted Jira to integrate with Flagsmith.

Describe alternatives you've considered

Do not support Jira on-prem

Additional context

N/a