Add tests for users and sessions

Split out common test infrastructure from security_templates_test, make
tests HTTPS, use the http.Client provided by httptest

internal/handlers/testdata_test.go

@@ -0,0 +1,39 @@
+package handlers_test
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+)
+
+// Needed because handlers.User doesn't allow Password to be written to JSON
+
+type User struct {
+	UserId          int64
+	DefaultCurrency int64 // SecurityId of default currency, or ISO4217 code for it if creating new user
+	Name            string
+	Username        string
+	Password        string
+	PasswordHash    string
+	Email           string
+}
+
+func (u *User) Write(w http.ResponseWriter) error {
+	enc := json.NewEncoder(w)
+	return enc.Encode(u)
+}
+
+func (u *User) Read(json_str string) error {
+	dec := json.NewDecoder(strings.NewReader(json_str))
+	return dec.Decode(u)
+}
+
+var users = []User{
+	User{
+		DefaultCurrency: 840, // USD
+		Name:            "John Smith",
+		Username:        "jsmith",
+		Password:        "hunter2",
+		Email:           "jsmith@example.com",
+	},
+}