refactor: canonical URL as path string

[davidlj95]

To avoid repeating new URL(path, APP_BASE_URL) around

Could be a feature of ngx-meta. Checkout davidlj95/ngx#252

Though to take into consideration that we have several emoji URLs whose canonical one is a string. Like /📅 canonical is /calendar. So could be useful to use a path as canonicalUrl in metadata. Then the library to read some APP_BASE_URL to form the proper URL.

[davidlj95]

Done in #1033