BAP to indicate elements needed with on_search/on_select/on_init/...

[venkatramanm]

When a bap fires a search, BPPs may return whatever they feel like (item_categories, provider catalog or just list of providers) but the BAP may expect certain elements to handle its UI Considerations. If there was a way to indicate the elements/fields BAP needs (kind of like graphql), BPP can make a more informed response.

Option 1:
BAP to form a json in the following fashion :
{
"json_path" : ["field1","field2",...]
}

for e.g
expectation = {
"./message/catalog" : [ "bpp/descriptor" , "bpp/fulfillments" , "bpp/providers" ]
"./message/catalog/bpp/providers[n]" : [ "items", "locations" ]
}
then pass in a header "X-ExpectedElements" : base64encoded(expectation)

BPPs can read and return accordingly.
Option2:
Another format could be like a template
expectation = {
"context" : {},
"message" : { "catalog" :
{ "bpp/descriptor" : {} ,
"bpp/providers" :[
{"locations" :[{ "id" :"" , "gps" : "" }],
"items":[{"id":"", "location_id":"", "descriptor": {} }]
}]
}
}
}
then pass in a header "X-ExpectedElements" : base64encoded(expectation)