feat(eventstore): sdk (#39)

* sdk

* fix(sdk): return correct error type

* AppendEventError instead of Aggregater error

* fix(tests): tests

* fix(tests): wantErr to is error func

internal/eventstore/sdk/append_event_error.go

@@ -0,0 +1,36 @@
+package sdk
+
+import (
+	"fmt"
+
+	"github.com/caos/zitadel/internal/errors"
+)
+
+var (
+	_ AppendEventError = (*appendEventError)(nil)
+	_ errors.Error     = (*appendEventError)(nil)
+)
+
+type AppendEventError interface {
+	error
+	IsAppendEventError()
+}
+
+type appendEventError struct {
+	*errors.CaosError
+}
+
+func ThrowAppendEventError(parent error, id, message string) error {
+	return &appendEventError{errors.CreateCaosError(parent, id, message)}
+}
+
+func ThrowAggregaterf(parent error, id, format string, a ...interface{}) error {
+	return ThrowAppendEventError(parent, id, fmt.Sprintf(format, a...))
+}
+
+func (err *appendEventError) IsAppendEventError() {}
+
+func IsAppendEventError(err error) bool {
+	_, ok := err.(AppendEventError)
+	return ok
+}