Update API v5 method coverage

[gwinn]

Added client methods:

• PaymentCheck: implements POST /api/v5/payment/check, sends PaymentCheckRequest as the check form field, and returns PaymentCheckResponse.
• PaymentCreateInvoice: implements POST /api/v5/payment/create-invoice, sends PaymentCreateInvoiceRequest as the createInvoice form field, and returns PaymentCreateInvoiceResponse.
• PaymentInvoiceImport: implements POST /api/v5/payment/invoice/import, sends PaymentInvoiceImportRequest as the invoice form field, and returns PaymentInvoiceResponse.
• PaymentInvoice: implements GET /api/v5/payment/invoice/{invoiceUuid} and returns PaymentInvoiceResponse.
• PaymentUpdateInvoice: implements POST /api/v5/payment/update-invoice, sends PaymentUpdateInvoiceRequest as the updateInvoice form field, and returns SuccessfulResponse.
• ProductsPropertiesValues: implements GET /api/v5/store/products/properties/values with propertyCode, propertyName, groups, limit, and page parameters.
• MGChannels: implements GET /api/v5/reference/mg-channels.
• Subscriptions: implements GET /api/v5/reference/subscriptions.
• SubscriptionEdit: implements POST /api/v5/reference/subscriptions/{channel}/{code}/edit and sends Subscription as the subscription form field.

Added request/filter/response DTOs:

• ProductsPropertiesValuesFilter and ProductsPropertiesValuesRequest for /api/v5/store/products/properties/values filtering and pagination.
• ProductsPropertiesValuesResponse for productPropertyValues payloads.
• PaymentCheckRequest and PaymentCheckResponse for payment check calls.
• PaymentCreateInvoiceRequest and PaymentCreateInvoiceResponse for payment invoice link creation.
• PaymentInvoiceImportRequest and PaymentInvoiceResponse for invoice import and invoice read calls.
• PaymentUpdateInvoiceRequest for invoice status/data updates.
• MGChannelsResponse for reference mgChannels payloads.
• SubscriptionsResponse for reference subscriptions payloads.

Changed and extended shared DTOs:

• Property: adds isNumeric, visible, and variative fields; fixes the sites JSON field name.
• ProductPropertyValue: adds a new DTO for property value rows returned by /api/v5/store/products/properties/values.
• Address: adds coordinates; Point is added for latitude/longitude.
• PaymentInvoice, PaymentInvoiceRefund, PaymentCheckResult, and PaymentCreateInvoiceResult are added for payment invoice APIs.
• PaymentType: fixes the paymentStatuses JSON field name.
• Site: adds senderEmail, senderName, and usedInSimlaweb.
• Store: adds ordering, contact, and optional workTime; WorkTimeByDay and StoreWorkTime are added for warehouse schedules.
• Integrations: adds recommendation, payment, and embedJs integration blocks.
• Delivery: adds duplicateOrderProductSupported and settings.
• DeliverySettings, DeliverySettingsPaymentType, DeliverySettingsShipmentPoint, and DeliverySettingsStatus are added for delivery integration configuration.
• Plate: adds type.
• DeliveryDataField: adds choices and visible.
• Recommendation and RecommendationMode are added for recommendation integrations.
• PaymentModule, PaymentModuleActions, and PaymentModuleShop are added for payment integrations.
• EmbedJS and EmbedJSPage are added for embedded JavaScript integration metadata.
• MgTransport: adds token and isActive.
• MgBot: adds isActive, logo, token, and name.

Comments and examples:

• Adds structured example comments for all newly added client methods.
• Adds missing structured example comments for existing reference API methods and MessageGateway template methods.
• Fixes the ProductsProperties example slice literal.

Tests:

• Adds coverage for PaymentCheck, PaymentCreateInvoice, PaymentInvoiceImport, PaymentInvoice, and PaymentUpdateInvoice.
• Adds coverage for ProductsPropertiesValues.
• Adds coverage for MGChannels, Subscriptions, and SubscriptionEdit.
• Keeps existing CustomersCombine and OrdersCombine behavior unchanged.

Backward compatibility:

• Potentially breaking: Property.Sites now uses JSON sites instead of the previous incorrect JSON Sites tag. Go field access remains Property.Sites, but exact JSON serialization/deserialization expectations using the uppercase key must be updated.
• Potentially breaking: PaymentType.PaymentStatuses now uses JSON paymentStatuses instead of the previous incorrect JSON PaymentStatuses tag. Go field access remains PaymentType.PaymentStatuses, but exact JSON payloads expecting the uppercase key must be updated.
• Store.WorkTime is added as an optional pointer field, so zero-value Store serialization remains compatible.
• All added methods and all other added DTO fields are additive and do not change existing method signatures.

Security:

• Update indirect dependency gopkg.in/yaml.v3 from v3.0.0-20200313102051-9f266ea9e77c to v3.0.1 to address the Dependabot security alert.