TTK-15369 Errors importing contents from K12

[rubenrua]

1.- Items with many urls.

PuMuKIT not implements import an object with several urls.

For example, see expressions/manifestations/items in https://oer.up2university.eu/search/v1/akif?set=UAL&q=Bonnie_Marranca_Part_1

"expressions": {
    "language": "en",
    "manifestations": {
        "items": [
            {
                "broken": false,
                "url":
    "http://ualresearchonline.arts.ac.uk/5119/1/rome.jpg"
            },
            {
                "broken": false,
                "url": "Stickland, Peter
    <http://ualresearchonline.arts.ac.uk/view/creators/Stickland=3APeter=3A=3A.html>
    and Toren, Amikam ..."
            },
            {
                "broken": false,
                "url": "http://ualresearchonline.arts.ac.uk/5119/"
            },
            {
                "broken": false,
                "url": "http://www.77books.co.uk/"
            }
        ],
    "format": "image"
}

2.- Unrecognized language:

K12 - DLESE catalogue has objects with a language format that is not recognized: en-US

The language format must be ISO 639-1 Code or ISO 639-2 Code.

Example:See expressions/language in https://oer.up2university.eu/search/v1/akif?set=DLESE&format=video.

When the next update, objects with unrecognized language will be convert to unknown language and not filtered.