[DOCS] Add jira auto-login with http headers documentation (#868)

* Add jira auto-login with http headers documentation

* Update two-factor-basic-auth.md

* Create using-remote-user-header-for-sso-with-jira.md

docs/community/using-remote-user-header-for-sso-with-jira.md

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+---
+layout: default
+title: Using Remote-User header for SSO with Jira
+parent: Community
+nav_order: 2
+---
+
+# Using Remote-User header for SSO with Jira
+
+You can make Jira auto-login to the user that is currently logged in to authelia.
+I say "auto-login" as I couldn't find any plugin to actually be authentication
+provider through HTTP headers only - LDAP though seems to have support.
+
+So this guide is targeted to authelia users that don't use any other authentication
+backend.
+
+I'm using traefik with docker as an example, but any proxy that can forward
+authelia `Remote-User` header is fine.
+
+First of all, users should exist on both authelia and Jira AND have the same
+username for this to work. Also you will have to [pay for a plugin](https://marketplace.atlassian.com/apps/1212581/easy-sso-jira-kerberos-ntlm-saml?hosting=server&tab=overview).
+
+After both steps are done:
+  - Add `traefik.http.middlewares.authelia.forwardauth.authResponseHeaders=Remote-User` in the labels of authelia
+  - Add `traefik.http.routers.jira.middlewares=authelia@docker` in the labels of Jira (to actually enable authelia for the jira instance)
+  - Install EasySSO in Jira
+  - Go to EasySSO preferences and add the "Remote-User" header under HTTP and tick the "Username" checkbox.
+  - Save
+
+## Other Systems
+
+While this guide is tailored for Jira, you can use a similar method with many other services like Jenkins and Grafana.