fix(go): disable strict validation and enable additional properties

[rubenhoenle]

Description

See https://openapi-generator.tech/docs/generators/go/

disallowAdditionalPropertiesIfNotPresent: If false, the 'additionalProperties' implementation (set to true by default) is compliant with the OAS and JSON schema specifications. If true (default), keep the old (incorrect) behaviour that 'additionalProperties' is set to false by default.

false: The 'additionalProperties' implementation is compliant with the OAS and JSON schema specifications.
true: Keep the old (incorrect) behaviour that 'additionalProperties' is set to false by default.

Changing this setting will cause the following changes in our SDK.

• Strict validation of API responses will be disabled (good for backward compatibility)
• Additional fields sent by the API are accessible in each response struct via a map

-       decoder := json.NewDecoder(bytes.NewReader(data))
-       decoder.DisallowUnknownFields()
-       err = decoder.Decode(&varUpdateVPNGatewayPayloadAvailabilityZones)
+       err = json.Unmarshal(data, &varUpdateVPNGatewayPayloadAvailabilityZones)

 type VPNTunnels struct {
        BgpStatus     NullableBGPStatus `json:"bgpStatus,omitempty"`
        InstanceState *GatewayStatus    `json:"instanceState,omitempty"`
        Name          *string           `json:"name,omitempty"`
        PublicIP      *string           `json:"publicIP,omitempty"`
+       AdditionalProperties map[string]interface{}
 }

Testing instructions

Generate the SDK with this bugfix. Look at the diff in sdk-repo-updated. Strict validation should be disabled as described above. AdditionalProperties map should be added to the structs.