Feat: Env variables to set health timeouts

- HEALTH_OPENVPN_DURATION_INITIAL
- HEALTH_OPENVPN_DURATION_ADDITION

internal/configuration/settings_test.go

@@ -37,6 +37,9 @@ func Test_Settings_lines(t *testing.T) {
 				"   |--Process user ID: 0",
 				"   |--Process group ID: 0",
 				"   |--Timezone: NOT SET ⚠️ - it can cause time related issues",
+				"|--Health:",
+				"   |--OpenVPN:",
+				"      |--Initial duration: 0s",
 				"|--HTTP control server:",
 				"   |--Listening port: 0",
 				"|--Public IP getter: disabled",