Discard empty and null links in Links fields (#12188)

This PR has several objectives:

- Ignore invalid and empty links in the frontend
- Ignore empty links when creating or updating a link field in the
backend
- Throw an error when trying to create or update a link field with an
invalid link

The logic is mostly the same in the frontend and the backend: we take
the initial primaryLink and the secondaryLinks, we discard all the empty
links (with `url === '' || url === null`), and the primaryLink becomes
the first remaining link.

## Frontend

There are three parts in the frontend where we have to remove the empty
links:

- LinksDisplay
- LinksFieldInput
- isFieldValueEmpty; used in RecordInlineCell

## Backend

I put the logic in
`packages/twenty-server/src/engine/core-modules/record-transformer/services/record-input-transformer.service.ts`
as it's used by the REST API, the GraphQL API, and by Create Record and
Update Record actions in the workflows.

packages/twenty-server/src/engine/metadata-modules/field-metadata/composite-types/links.composite-type.ts

@@ -37,3 +37,8 @@ export type LinksMetadata = {
   primaryLinkUrl: string;
   secondaryLinks: LinkMetadata[] | null;
 };
+
+export type LinkMetadataNullable = {
+  label: string | null;
+  url: string | null;
+};