Add capture_type property support to Static Liveness resources

[Copilot]

The Static Liveness resource response was missing the capture_type property that indicates the type of capture performed (e.g., SELFIE, ID_DOCUMENT).

Changes

• StaticLivenessResourceResponse: Added CaptureType field to expose the property when fetching session resources
• BaseRequiredResource: Added CaptureType field to support the property in required resources flow
• Test coverage: Updated fixtures and assertions to verify property parsing

The field uses omitempty for backward compatibility with existing integrations.

type StaticLivenessResourceResponse struct {
    *LivenessResourceResponse
    Image       *Image `json:"image"`
    CaptureType string `json:"capture_type,omitempty"`  // New field
}

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