dnsdist: Refactor DoH prometheus metrics again

[rgacogne]

Short description

dnsdist_frontend_tlsnewsessions{frontend="127.0.0.1:9443",proto="TCP (DNS over HTTPS)"} 0
dnsdist_frontend_tlsresumptions{frontend="127.0.0.1:9443",proto="TCP (DNS over HTTPS)"} 0
# HELP dnsdist_frontend_http_connects Number of DoH TCP connections established to this frontend
# TYPE dnsdist_frontend_http_connects counter
# HELP dnsdist_frontend_doh_tls_queries Number of DoH queries received by dnsdist, by TLS version
# TYPE dnsdist_frontend_doh_tls_queries counter
# HELP dnsdist_frontend_doh_http_method_queries Number of DoH queries received by dnsdist, by HTTP method
# TYPE dnsdist_frontend_doh_http_method_queries counter
# HELP dnsdist_frontend_doh_http_version_queries Number of DoH queries received by dnsdist, by HTTP version
# TYPE dnsdist_frontend_doh_http_version_queries counter
# HELP dnsdist_frontend_doh_bad_requests Number of requests that could not be converted to a DNS query
# TYPE dnsdist_frontend_doh_bad_requests counter
# HELP dnsdist_frontend_doh_responses Number of responses sent, by type
# TYPE dnsdist_frontend_doh_responses counter
# HELP dnsdist_frontend_doh_version_status_responses Number of requests that could not be converted to a DNS query
# TYPE dnsdist_frontend_doh_version_status_responses counter
dnsdist_frontend_http_connects{address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_tls_queries{tls="tls10",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_tls_queries{tls="tls11",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_tls_queries{tls="tls12",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_tls_queries{tls="tls13",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_tls_queries{tls="unknown",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_http_method_queries{method="get",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_http_method_queries{method="post",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_http_version_queries{version="1",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_http_version_queries{version="2",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_bad_requests{address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_responses{type="error",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_responses{type="redirect",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_responses{type="valid",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="1",status="200",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="1",status="400",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="1",status="403",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="1",status="500",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="1",status="502",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="1",status="other",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="2",status="200",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="2",status="400",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="2",status="403",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="2",status="500",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="2",status="502",address="127.0.0.1:9443" } 0
dnsdist_frontend_doh_version_status_responses{httpversion="2",status="other",address="127.0.0.1:9443" } 0

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)