Use correspondence attachment id for download attachment

[Andreass2]

Description

Features:

• Use correspondence attachment id for download attachment
• Update swagger documentation
• Add Correspondence Ids to attachment details/overview

Fixes:

• Fix problem with data location url not beeing present in overview/details
• DataLocationUrl had wrong type in AttachmentOverviewExt

Related Issue(s)

• Replace AttachmentId with CorrespondenceAttachmendId in AttachmentController #104

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)
• All tests run green

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[Ceredron]

Looks good!
Remember to update spec with new correspondenceIds:
https://github.com/Altinn/altinn-studio-docs/blob/master/static/swagger/altinn-broker-v1.json