'origin not allowed' error after upgrading to PMM 2.27.0 when using reverse proxy

In PMM server 2.27.0, we upgraded the nginx config:

https://github.com/percona/pmm-update/commit/bda2b8d8af986a06f1855986ac61cdde4d6808be

If a customer uses a reverse proxy (for example, nginx), it can be the cause of the issue with dashboards:

origin not allowed

because Host header will be empty.

How to fix

We need to add Host header to the reverse proxy config. For example for nginx:

proxy_set_header Host $http_host;

(It's a good idea to add this information to RN)