EOProduct asset improvements

[alambare-csgroup]

Standardize the data exposition in EO Products:

• make sure we include the "downloadLink" as an asset in EOProduct for every plugins
• configure it using something like:

        assets: >
          {$.assets#dict_update(
            [["downloadLink",[
              ["title","Full product download"],
              ["href","{downloadLink}"],
              ["roles",["data"]],
              ["type","application/zip"]
              ["order",[
                ["href","{orderLink}"],
                ["method","POST"],
                ["body",[
                  ["foo","bar"],
                ]],
              ]]
            ]]])
          }

• downloadLink does not reflect clearly the content of the asset. Call the "downloadLink" asset "data" instead. The description should be adapted to the content and format of the asset

Assets returned are not always retrievable using a GET request. We should also support POST method.

• For POST requests, add a method property in the asset with value set to POST. If not set we assume the request is GET

Some asset requests require a body like the datacubes datasets for example. At the moment, the body is added to the query params of the asset URL.

• if the request requires a body, add a body property to the asset with the body value