Purevpn support (#208)

Fixes #192

internal/params/purevpn.go

@@ -0,0 +1,26 @@
+package params
+
+import (
+	"github.com/qdm12/private-internet-access-docker/internal/constants"
+)
+
+// GetPurevpnRegion obtains the region (continent) for the PureVPN server from the
+// environment variable REGION
+func (r *reader) GetPurevpnRegion() (region string, err error) {
+	choices := append(constants.PurevpnRegionChoices(), "")
+	return r.envParams.GetValueIfInside("REGION", choices)
+}
+
+// GetPurevpnCountry obtains the country for the PureVPN server from the
+// environment variable COUNTRY
+func (r *reader) GetPurevpnCountry() (country string, err error) {
+	choices := append(constants.PurevpnCountryChoices(), "")
+	return r.envParams.GetValueIfInside("COUNTRY", choices)
+}
+
+// GetPurevpnCity obtains the city for the PureVPN server from the
+// environment variable CITY
+func (r *reader) GetPurevpnCity() (city string, err error) {
+	choices := append(constants.PurevpnCityChoices(), "")
+	return r.envParams.GetValueIfInside("CITY", choices)
+}