feat: add stdout and filesystem notification channels (#2925)

* feat: add filesystem and stdout notification channels

* configure through env vars

* compile

* feat: add compact option for debug notification channels

* fix channel mock generation

* avoid sensitive information in error message

Co-authored-by: Livio Amstutz <livio.a@gmail.com>

* add review improvements

Co-authored-by: Livio Amstutz <livio.a@gmail.com>

internal/notification/channels/mock/message.mock.go

@@ -0,0 +1,47 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/caos/zitadel/internal/notification/channels (interfaces: Message)
+
+// Package mock is a generated GoMock package.
+package mock
+
+import (
+	gomock "github.com/golang/mock/gomock"
+	reflect "reflect"
+)
+
+// MockMessage is a mock of Message interface
+type MockMessage struct {
+	ctrl     *gomock.Controller
+	recorder *MockMessageMockRecorder
+}
+
+// MockMessageMockRecorder is the mock recorder for MockMessage
+type MockMessageMockRecorder struct {
+	mock *MockMessage
+}
+
+// NewMockMessage creates a new mock instance
+func NewMockMessage(ctrl *gomock.Controller) *MockMessage {
+	mock := &MockMessage{ctrl: ctrl}
+	mock.recorder = &MockMessageMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use
+func (m *MockMessage) EXPECT() *MockMessageMockRecorder {
+	return m.recorder
+}
+
+// GetContent mocks base method
+func (m *MockMessage) GetContent() string {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetContent")
+	ret0, _ := ret[0].(string)
+	return ret0
+}
+
+// GetContent indicates an expected call of GetContent
+func (mr *MockMessageMockRecorder) GetContent() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetContent", reflect.TypeOf((*MockMessage)(nil).GetContent))
+}