Bugfix - Enforce URL length check in LinkMetadata before attempting to insert to database (#29589)

* Add missing URL length validation in LinkMetadata

* Added MaxURLLength constant

* Add test to validate new URL length limit

* Add comment about table constraint

* Use a seperate error string for URL length errors

* Added error string fpr URL length

* Updated error message

* Update en.json

* Fixed gofmt error in link_metadata.go

* use right txn id

```release-note
NONE
```

---------

Co-authored-by: Agniva De Sarker <agnivade@yahoo.co.in>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/i18n/en.json

@@ -9520,6 +9520,10 @@
     "id": "model.link_metadata.is_valid.url.app_error",
     "translation": "Link metadata URL must be set."
   },
+  {
+    "id": "model.link_metadata.is_valid.url_length.app_error",
+    "translation": "Length of link metadata URL is {{ .Length }} characters long, which exceeds the maximum limit of {{ .MaxLength }} characters."
+  },
   {
     "id": "model.member.is_valid.channel.app_error",
     "translation": "Channel name is not valid"

server/public/model/link_metadata.go

@@ -21,6 +21,7 @@ const (
 	LinkMetadataTypeNone      LinkMetadataType = "none"
 	LinkMetadataTypeOpengraph LinkMetadataType = "opengraph"
 	LinkMetadataMaxImages     int              = 5
+	LinkMetadataMaxURLLength  int              = 2048 // Maximum URL length in LinkMetadata table
 )
 
 type LinkMetadataType string
@@ -93,6 +94,10 @@ func (o *LinkMetadata) IsValid() *AppError {
 		return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.url.app_error", nil, "", http.StatusBadRequest)
 	}
 
+	if len(o.URL) > LinkMetadataMaxURLLength {
+		return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.url_length.app_error", map[string]any{"MaxLength": LinkMetadataMaxURLLength, "Length": len(o.URL)}, "", http.StatusBadRequest)
+	}
+
 	if o.Timestamp == 0 || !isRoundedToNearestHour(o.Timestamp) {
 		return NewAppError("LinkMetadata.IsValid", "model.link_metadata.is_valid.timestamp.app_error", nil, "", http.StatusBadRequest)
 	}

server/public/model/link_metadata_test.go

@@ -146,6 +146,16 @@ func TestLinkMetadataIsValid(t *testing.T) {
 			},
 			Expected: false,
 		},
+		{
+			Name: "should be invalid because of URL length being too long",
+			Metadata: &LinkMetadata{
+				URL:       "http://example.com/?" + strings.Repeat("a", 2048),
+				Timestamp: 1546300800000,
+				Type:      LinkMetadataTypeImage,
+				Data:      &PostImage{},
+			},
+			Expected: false,
+		},
 	} {
 		t.Run(test.Name, func(t *testing.T) {
 			appErr := test.Metadata.IsValid()