Edge browser: support items to get the signatures of an edge

[melisabok]

Currently the edge browser only support API 1 invitation schema.

I suggest to change the logic so the UI can load the signatures from the items keyword and we don't need to use a regex with pipes.

I can provide a test in openreview-py

[xkopenreview]

should it also support enum array enum object? or it will always use items

[melisabok]

AFAIK we should always use items for signatures, right?

[xkopenreview]

i think converting some groups to items can potentially get 10x more groups than required.
for example to get groups for

NeurIPS.cc/2023/Conference/Submission.*/Area_Chair_.*

it can only get groups using the prefix

NeurIPS.cc/2023/Conference/Submission.*

and filter in edge browser for those ends with Area_Chair_.*

which returns about ten time more groups compares to regex pipe

[melisabok]

I think the API call to get the signature groups should be done at the moment of editing the edge.

[melisabok]

Can the regex to be like?:

NeurIPS.cc/2023/Conference/Submission${6/head/number}/Area_Chair_.*

I think the UI can replace the dollar sign and get the group by prefix.

[melisabok]

Use this PR to test it: openreview/openreview-py#1965