feat: integrate restcountries api

internal/geodata/models.go

@@ -0,0 +1,19 @@
+package geodata
+
+// Country info exposed to other packages
+type Country struct {
+	Name       string
+	Population int64
+}
+
+// Timezone to Country lookups
+type TimezoneMap map[string][]Country
+
+// internal model for https://restcountries.com/v3.1/all?fields=name,population,timezones
+type countryApiReponse struct {
+	Name struct {
+		Common string `json:"common"` // it has other fields but I don't want them
+	} `json:"name"`
+	Population int64    `json:"population"`
+	Timezones  []string `json:"timezones"` // example: [ "UTC+00:00" ]
+}