feat(api): add ivr.proto (#727)

docs/en/design/notify/phone_call.md

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+# PhoneCall API design
+
+## What would you like to be added
+IVR API, or PhoneCall API
+
+Developers can invoke this API to send voice messages to specific people.
+
+## Why is this needed
+In the monitoring scenarios, monitor systems need to send alarm messages to people on-call.
+The messages might be in different forms, including IM,SMS, Email and phone calls, depending on the level of urgency.
+
+## Product research
+| IVR product |Docs|
+|---|---|
+|Aliyun VMS| https://www.aliyun.com/product/vms |
+|AWS Pinpoint | https://aws.amazon.com/cn/pinpoint/ |
+
+
+## Detailed Design
+
+We need to consider the following factors:
+- Portability
+  For example, a monitor system might be deployed on alibaba cloud(using [VMS](https://www.aliyun.com/product/vms) to send voice message) or AWS (using [AWS Pinpoint](https://aws.amazon.com/cn/pinpoint/)  to send voice message). So portability is important here.
+
+```proto
+// PhoneCallService is one of Notify APIs. It's used to send voice messages
+service PhoneCallService {
+
+  // Send voice using the specific template
+  rpc SendVoiceWithTemplate(SendVoiceWithTemplateRequest) returns (SendVoiceWithTemplateResponse) {}
+
+}
+
+// The request of SendVoiceWithTemplate method
+message SendVoiceWithTemplateRequest{
+
+  // If your system uses multiple IVR services at the same time,
+  // you can specify which service to use with this field.
+  string service_name = 1;
+
+  // Required
+  VoiceTemplate template = 2;
+
+  // Required
+  repeated string to_mobile = 3;
+
+  // This field is required by some cloud providers.
+  string from_mobile = 4;
+
+}
+
+// VoiceTemplate
+message VoiceTemplate{
+
+  // Required
+  string template_id = 1;
+
+  // Required
+  map<string, string>  template_params = 2;
+
+}
+
+// The response of `SendVoiceWithTemplate` method
+message SendVoiceWithTemplateResponse{
+
+  // Id of this request.
+  string request_id = 1;
+
+}
+
+```

spec/proto/runtime/v1/phone_call.proto

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+syntax = "proto3";
+
+package spec.proto.runtime.v1;
+
+import "google/protobuf/empty.proto";
+import "google/protobuf/any.proto";
+
+option go_package = "mosn.io/layotto/spec/proto/runtime/v1;runtime";
+
+// PhoneCallService is one of Notify APIs. It's used to send voice messages
+service PhoneCallService {
+
+  // Send voice using the specific template
+  rpc SendVoiceWithTemplate(SendVoiceWithTemplateRequest) returns (SendVoiceWithTemplateResponse) {}
+
+}
+
+// The request of SendVoiceWithTemplate method
+message SendVoiceWithTemplateRequest{
+
+  // If your system uses multiple IVR services at the same time,
+  // you can specify which service to use with this field.
+  string service_name = 1;
+
+  // Required
+  VoiceTemplate template = 2;
+
+  // Required
+  repeated string to_mobile = 3;
+
+  // This field is required by some cloud providers.
+  string from_mobile = 4;
+
+}
+
+// VoiceTemplate
+message VoiceTemplate{
+
+  // Required
+  string template_id = 1;
+
+  // Required
+  map<string, string>  template_params = 2;
+
+}
+
+// The response of `SendVoiceWithTemplate` method
+message SendVoiceWithTemplateResponse{
+
+  // Id of this request.
+  string request_id = 1;
+
+}