directory/azure: add paging support to user group members call (#2311)

internal/directory/azure/api.go

@@ -0,0 +1,45 @@
+package azure
+
+import "strings"
+
+type (
+	apiGetUserResponse struct {
+		apiUser
+	}
+	apiGetUserMembersResponse struct {
+		Context  string     `json:"@odata.context"`
+		NextLink string     `json:"@odata.nextLink,omitempty"`
+		Value    []apiGroup `json:"value"`
+	}
+
+	apiGroup struct {
+		ID          string `json:"id"`
+		DisplayName string `json:"displayName"`
+	}
+	apiUser struct {
+		ID                string `json:"id"`
+		DisplayName       string `json:"displayName"`
+		Mail              string `json:"mail"`
+		UserPrincipalName string `json:"userPrincipalName"`
+	}
+)
+
+func (obj apiUser) getEmail() string {
+	if obj.Mail != "" {
+		return obj.Mail
+	}
+
+	// AD often doesn't have the email address returned, but we can parse it from the UPN
+
+	// UPN looks like:
+	// cdoxsey_pomerium.com#EXT#@cdoxseypomerium.onmicrosoft.com
+	email := obj.UserPrincipalName
+	if idx := strings.Index(email, "#EXT"); idx > 0 {
+		email = email[:idx]
+	}
+	// find the last _ and replace it with @
+	if idx := strings.LastIndex(email, "_"); idx > 0 {
+		email = email[:idx] + "@" + email[idx+1:]
+	}
+	return email
+}