Turnpike 1.5.0

What's Changed

• nginx and nginx-prometheus images upgrade by @petracihalova in #103
• bump python version into 3.9 + bump dependencies to the highest versions by @petracihalova in #102
• set base image tag in Dockerfiles by @petracihalova in #109
• Fix x-rh-identity header encoding by @kahowell in #110
• updated Grafana Dashboard for Turnpike by @petracihalova in #111
• updated Grafana Dashboard for Turnpike - fixed 'Status code proportion' panel by @petracihalova in #112

Full Changelog: v1.4.0...v1.5.0