[Feature](dns): improve UI when creating multiple DNS records

[SuperSandro2000]

Description
The content field defined here

elektra/plugins/dns_service/app/views/dns_service/zones/recordsets/new.html.haml

Line 35 in c9ed405

label: label_values[:label] || 'Content',

for DNS/Designate should not forward the suboptimal UX of multiple records with the same name from the designate API to the end user.

Problem Statement
Having to quote records and placing commas between them is bad UX.

Proposed Solution
Replace the text box with a list which automatically expands/decreases to one empty line at the end and allows the end user to easily configure multiple records without having to write a CSV by hand.

Alternatives Considered

Additional Context
Add any other context or information here.