Publish price as in new DFC standard

[mkllnk]

What? Why?

I noticed that our API documentation was out of date and we didn't publish prices correctly.

The change may affect API integrations that read prices from the OFN catalog. An offer's price attribute is now an object with currency instead of just a number value:

-                      dfc-b:hasPrice: 19.99
+                      dfc-b:hasPrice:
+                        "@type": dfc-b:Price
+                        dfc-b:value: 19.99
+                        dfc-b:hasUnit: dfc-m:AUD

What should we test?

• Specs only.

Release notes

Changelog Category (reviewers may add a label for the release notes):

• User facing changes
• API changes (V0, V1, DFC or Webhook)
• Technical changes only
• Feature toggled

The title of the pull request will be included in the release notes.

Dependencies

Documentation updates

[RachL]

@mkllnk does this impact the affliatedsalesdata endpoint? (no worries if it does, I just need to warn the users)

[mkllnk]

does this impact the affliatedsalesdata endpoint?

No. I kept that one the same.