[MM-62427] Add message attachments validation (#30180)

* Add message attachments validation

* Add props validation

* Validate slack attachment fields

* Update tests and library usage

* Improve interactive dialog error for length checks

* Allow predefined colors for slack attachments

* Fix TestPostAction

* Use const for data source

* Add tests

* Cleanup unused props

* Add happy path tests

* lint fixes

* Add validation for PostActionOptions

server/public/model/slack_attachment_test.go

@@ -9,6 +9,165 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestSlackAttachment_IsValid(t *testing.T) {
+	tests := map[string]struct {
+		attachment *SlackAttachment
+		wantErr    string
+	}{
+		"valid attachment": {
+			attachment: &SlackAttachment{
+				Text: "This is a test",
+			},
+			wantErr: "",
+		},
+		"invalid color": {
+			attachment: &SlackAttachment{
+				Color: "invalid",
+			},
+			wantErr: "invalid style 'invalid' - must be one of [good, warning, danger] or a hex color",
+		},
+		"valid predefined color": {
+			attachment: &SlackAttachment{
+				Color: "good",
+			},
+			wantErr: "",
+		},
+		"valid warning color": {
+			attachment: &SlackAttachment{
+				Color: "warning",
+			},
+			wantErr: "",
+		},
+		"valid danger color": {
+			attachment: &SlackAttachment{
+				Color: "danger",
+			},
+			wantErr: "",
+		},
+		"valid hex color": {
+			attachment: &SlackAttachment{
+				Color: "#FF0000",
+			},
+			wantErr: "",
+		},
+		"author link without name": {
+			attachment: &SlackAttachment{
+				AuthorLink: "http://example.com",
+			},
+			wantErr: "author link cannot be set without author name",
+		},
+		"invalid author link": {
+			attachment: &SlackAttachment{
+				AuthorName: "Author",
+				AuthorLink: "invalid-url",
+			},
+			wantErr: "invalid author link URL",
+		},
+		"invalid author icon": {
+			attachment: &SlackAttachment{
+				AuthorIcon: "invalid-url",
+			},
+			wantErr: "invalid author icon URL",
+		},
+		"title link without title": {
+			attachment: &SlackAttachment{
+				TitleLink: "http://example.com",
+			},
+			wantErr: "title link cannot be set without title",
+		},
+		"invalid title link": {
+			attachment: &SlackAttachment{
+				Title:     "Title",
+				TitleLink: "invalid-url",
+			},
+			wantErr: "invalid title link URL",
+		},
+		"invalid image URL": {
+			attachment: &SlackAttachment{
+				ImageURL: "invalid-url",
+			},
+			wantErr: "invalid image URL",
+		},
+		"invalid thumb URL": {
+			attachment: &SlackAttachment{
+				ThumbURL: "invalid-url",
+			},
+			wantErr: "invalid thumb URL",
+		},
+		"invalid footer icon": {
+			attachment: &SlackAttachment{
+				FooterIcon: "invalid-url",
+			},
+			wantErr: "invalid footer icon URL",
+		},
+		"invalid timestamp type": {
+			attachment: &SlackAttachment{
+				Timestamp: []string{"invalid"},
+			},
+			wantErr: "timestamp must be either a string or int64",
+		},
+		"valid timestamp string": {
+			attachment: &SlackAttachment{
+				Timestamp: "1234567890",
+			},
+			wantErr: "",
+		},
+		"valid timestamp int64": {
+			attachment: &SlackAttachment{
+				Timestamp: int64(1234567890),
+			},
+			wantErr: "",
+		},
+		"invalid action": {
+			attachment: &SlackAttachment{
+				Actions: []*PostAction{
+					{
+						Name: "", // Invalid - missing name
+					},
+				},
+			},
+			wantErr: "action must have a name",
+		},
+		"invalid field value type": {
+			attachment: &SlackAttachment{
+				Fields: []*SlackAttachmentField{
+					{
+						Title: "Title",
+						Value: []string{"invalid"},
+					},
+				},
+			},
+			wantErr: "value must be either a string or int",
+		},
+		"valid fields": {
+			attachment: &SlackAttachment{
+				Fields: []*SlackAttachmentField{
+					{
+						Title: "Title",
+						Value: "string value",
+					},
+					{
+						Title: "Number",
+						Value: 42,
+					},
+				},
+			},
+			wantErr: "",
+		},
+	}
+
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			err := tc.attachment.IsValid()
+			if tc.wantErr == "" {
+				assert.NoError(t, err, name)
+			} else {
+				assert.ErrorContains(t, err, tc.wantErr, name)
+			}
+		})
+	}
+}
+
 func TestParseSlackAttachment(t *testing.T) {
 	t.Run("empty list", func(t *testing.T) {
 		post := &Post{}
@@ -19,7 +178,7 @@ func TestParseSlackAttachment(t *testing.T) {
 		expectedPost := &Post{
 			Type: PostTypeSlackAttachment,
 			Props: map[string]any{
-				"attachments": []*SlackAttachment{},
+				PostPropsAttachments: []*SlackAttachment{},
 			},
 		}
 		assert.Equal(t, expectedPost, post)
@@ -36,7 +195,7 @@ func TestParseSlackAttachment(t *testing.T) {
 		expectedPost := &Post{
 			Type: PostTypeSlackAttachment,
 			Props: map[string]any{
-				"attachments": []*SlackAttachment{},
+				PostPropsAttachments: []*SlackAttachment{},
 			},
 		}
 		assert.Equal(t, expectedPost, post)