Add proto rpc interface for cli

This commit adds proto rpc definitions for the communication needed for
the CLI interface.
This will allow us to move the rest of the CLI interface over to gRPC
and in the future allow remote access

proto/headscale/v1/preauthkey.proto

@@ -0,0 +1,43 @@
+syntax = "proto3";
+package headscale.v1;
+option  go_package = "github.com/juanfont/headscale/gen/go/v1";
+
+import "google/protobuf/timestamp.proto";
+
+message PreAuthKey {
+    string namespace                     = 1;
+    string                    id         = 2;
+    string                    key        = 3;
+    bool                      resuable   = 4;
+    bool                      ephemeral  = 5;
+    bool                      used       = 6;
+    google.protobuf.Timestamp expiration = 7;
+    google.protobuf.Timestamp created_at = 8;
+}
+
+message CreatePreAuthKeyRequest {
+    string namespace                     = 1;
+    bool                      resuable   = 2;
+    bool                      ephemeral  = 3;
+    google.protobuf.Timestamp expiration = 4;
+}
+
+message CreatePreAuthKeyResponse {
+    PreAuthKey pre_auth_key = 1;
+}
+
+message ExpirePreAuthKeyRequest {
+    string namespace = 1;
+    string key       = 2;
+}
+
+message ExpirePreAuthKeyResponse {
+}
+
+message ListPreAuthKeysRequest {
+    string namespace = 1;
+}
+
+message ListPreAuthKeysResponse {
+    repeated PreAuthKey pre_auth_keys = 1;
+}