RelatedUrls description #332

Describe the bug
For the RelatedUrls, a unique description has to be provided for each url. Currently, the metadata element 'RelatedUrls/Description' is missing in the umm-c schema. There are two conditions that needs to be tested for this field.
First, you need to check if the description is present or not. If there are no description, we should have the following message "Recommend providing a description for each URL".
Second, you need to check if there are duplicate descriptions for the field. Then, it is suggested that we have the following recommendation messages. "Descriptions should be unique to each URL. Several of the descriptions are repeated in this record. Recommend changing the descriptions to more accurately and uniquely describe each link"

To Reproduce
Test the following records in the master branch.

C1000000011-CDDIS and C1000000005-CDDIS (umm-c) - Missing description
C1544926730-CDDIS (umm-c) - Identical descriptions

Expected behavior
For the first scenario having missing description, you need to have one recommendation, whereas for the second scenario having identical description, you need to provide two recommendations.