fix: provide a proper error message when viewing a link share with an invalid token

docs/content/doc/usage/errors.md

@@ -162,7 +162,8 @@ This document describes the different errors Vikunja can return.
 
 ## Link Shares
 
-| ErrorCode | HTTP Status Code | Description |
-|-----------|------------------|-------------|
+| ErrorCode | HTTP Status Code | Description                                                                    |
+|-----------|------------------|--------------------------------------------------------------------------------|
 | 13001 | 412 | This link share requires a password for authentication, but none was provided. |
-| 13002 | 403 | The provided link share password was invalid. |
+| 13002 | 403 | The provided link share password is invalid.                                   |
+| 13003 | 400 | The provided link share token is invalid.                                      |

pkg/models/error.go

@@ -1709,3 +1709,29 @@ func (err ErrLinkSharePasswordInvalid) HTTPError() web.HTTPError {
 		Message:  "The provided link share password is invalid.",
 	}
 }
+
+// ErrLinkShareTokenInvalid represents an error where a link share token is invalid
+type ErrLinkShareTokenInvalid struct {
+}
+
+// IsErrLinkShareTokenInvalid checks if an error is ErrLinkShareTokenInvalid.
+func IsErrLinkShareTokenInvalid(err error) bool {
+	_, ok := err.(*ErrLinkShareTokenInvalid)
+	return ok
+}
+
+func (err *ErrLinkShareTokenInvalid) Error() string {
+	return "Provided Link Share Token is invalid"
+}
+
+// ErrCodeLinkShareTokenInvalid holds the unique world-error code of this error
+const ErrCodeLinkShareTokenInvalid = 13003
+
+// HTTPError holds the http error description
+func (err ErrLinkShareTokenInvalid) HTTPError() web.HTTPError {
+	return web.HTTPError{
+		HTTPCode: http.StatusBadRequest,
+		Code:     ErrCodeLinkShareTokenInvalid,
+		Message:  "The provided link share token is invalid.",
+	}
+}

pkg/models/link_sharing.go

@@ -86,10 +86,15 @@ func (share *LinkSharing) GetID() int64 {
 
 // GetLinkShareFromClaims builds a link sharing object from jwt claims
 func GetLinkShareFromClaims(claims jwt.MapClaims) (share *LinkSharing, err error) {
+	projectID, is := claims["project_id"].(float64)
+	if !is {
+		return nil, &ErrLinkShareTokenInvalid{}
+	}
+
 	share = &LinkSharing{}
 	share.ID = int64(claims["id"].(float64))
 	share.Hash = claims["hash"].(string)
-	share.ProjectID = int64(claims["project_id"].(float64))
+	share.ProjectID = int64(projectID)
 	share.Right = Right(claims["right"].(float64))
 	share.SharedByID = int64(claims["sharedByID"].(float64))
 	return