Links custom field

[stbnrivas]

I would like propose to talk about new type of custom_field for link

1. a link should be two inputs

• link display value
• link url

2. I am not sure if it useful localized the custom field:

• localized_link_to
• link_to

3. stuff which involve

• custom_field_type
• custom_field_validation

[ferblape]

Take care with the details (start the issue title in capital letters, be a bit more verbose) and ortography. This is what I'd had written in the issue:

Title: Links custom field

In order to support linked text in custom fields (i.e a field linking to the original source of a dataset as required in #3032) there are two options:

1. implement a new type of custom field to support HTML links, composed by two attributes a text and a link (the href attribute of the link)
2. use a String custom field and use HTML on its value:
   

While this second option is a quick solution, it's not very elegant. If we foresee that a link custom field might be useful in the future I'd suggest to add it now and prevent any data migration in the future. Otherwise we might solve the current needs with a raw string custom field.

cc @furilo