Remove decomissioned SecureDNS (#49)

Author: axel-dd

README.md

@@ -25,7 +25,6 @@
     - [Cloudflare](https://developers.cloudflare.com/1.1.1.1/dns-over-tls/)
     - [Google](https://developers.google.com/speed/public-dns/docs/dns-over-tls)
     - [Quad9](https://www.quad9.net/faq/#Does_Quad9_support_DNS_over_TLS)
-    - [SecureDNS](https://securedns.eu)
     - [LibreDNS](https://libredns.gr)
     - [Quadrant](https://quadrantsec.com/about/blog/quadrants_public_dns_resolver_with_tls_https_support/)
     - [CleanBrowsing](https://cleanbrowsing.org/guides/dnsovertls)
@@ -79,7 +78,7 @@ Diagrams are shown for router and client-by-client configurations in the [**Conn
 
 | Environment variable | Default | Description |
 | --- | --- | --- |
-| `PROVIDERS` | `cloudflare` | Comma separated list of DNS-over-TLS providers from `cloudflare`, `google`, `quad9`, `quadrant`, `cleanbrowsing`, `securedns`, `libredns` and `cira` |
+| `PROVIDERS` | `cloudflare` | Comma separated list of DNS-over-TLS providers from `cloudflare`, `google`, `quad9`, `quadrant`, `cleanbrowsing`, `libredns` and `cira` |
 | `VERBOSITY` | `1` | From 0 (no log) to 5 (full debug log) |
 | `VERBOSITY_DETAILS` | `0` | From 0 to 4 (higher means more details) |
 | `BLOCK_MALICIOUS` | `on` | `on` or `off`, to block malicious IP addresses and malicious hostnames from being resolved |

internal/constants/dns.go

@@ -17,8 +17,6 @@ const (
 	Quadrant models.Provider = "quadrant"
 	// CleanBrowsing is a DNS over TLS provider.
 	CleanBrowsing models.Provider = "cleanbrowsing"
-	// SecureDNS is a DNS over TLS provider.
-	SecureDNS models.Provider = "securedns"
 	// LibreDNS is a DNS over TLS provider.
 	LibreDNS models.Provider = "libredns"
 	// CIRA is a DNS over TLS provider.
@@ -55,11 +53,6 @@ func ProviderMapping() map[models.Provider]models.ProviderData {
 			SupportsIPv6: true,
 			Host:         models.Host("security-filter-dns.cleanbrowsing.org"),
 		},
-		SecureDNS: {
-			IPs:          []net.IP{{146, 185, 167, 43}, {0x2a, 0x3, 0xb0, 0xc0, 0x0, 0x0, 0x10, 0x10, 0x0, 0x0, 0x0, 0x0, 0xe, 0x9a, 0x30, 0x1}},
-			SupportsIPv6: true,
-			Host:         models.Host("dot.securedns.eu"),
-		},
 		LibreDNS: {
 			IPs:  []net.IP{{116, 202, 176, 26}},
 			Host: models.Host("dot.libredns.gr"),