rekor-cli: intersection vs union search

[di]

Description

Currently if I provide multiple search flags to rekor-cli search, I get the union of results with those individual terms (without duplicates removed):

$ rekor-cli search --sha `sha256sum hi.txt`
Found matching entries (listed by UUID):
5dbf6d1b87e46f0bdf218c42befffd9a77dc678fc6868ee63f97db6145db4625

$ rekor-cli search --email di@python.org
Found matching entries (listed by UUID):
5dbf6d1b87e46f0bdf218c42befffd9a77dc678fc6868ee63f97db6145db4625
00f1e767aea63eeec6f01005c7a9a6b0eb578a77ebc6a0dc3f4798a172d7562b
3c2ebb9e75bf89efeb52e2a465ad57c0f93f4d86c2aca63f42a1d2f34a835226
89473f4630b65edef4927dc5f02f8e810325455087297d8d1dec8998127f2420
19700e194c143e7aedb379004330f7636fa76afff4f59fcea2ed762412299ab7

$ rekor-cli search --sha `sha256sum hi.txt` --email di@python.org
Found matching entries (listed by UUID):
5dbf6d1b87e46f0bdf218c42befffd9a77dc678fc6868ee63f97db6145db4625
5dbf6d1b87e46f0bdf218c42befffd9a77dc678fc6868ee63f97db6145db4625
00f1e767aea63eeec6f01005c7a9a6b0eb578a77ebc6a0dc3f4798a172d7562b
3c2ebb9e75bf89efeb52e2a465ad57c0f93f4d86c2aca63f42a1d2f34a835226
89473f4630b65edef4927dc5f02f8e810325455087297d8d1dec8998127f2420
19700e194c143e7aedb379004330f7636fa76afff4f59fcea2ed762412299ab7

It'd be helpful to be able to provide a flag which switches this from the implicit OR to an explicit AND operator, something like:

$ rekor-cli search --operator AND --sha `sha256sum hi.txt` --email di@python.org
Found matching entries (listed by UUID):
5dbf6d1b87e46f0bdf218c42befffd9a77dc678fc6868ee63f97db6145db4625

As a workaround for now, folks can do something like:

$ comm -12 <(rekor-cli search --sha `sha256sum hi.txt` | sort) <(rekor-cli search --email di@python.org | sort)
Found matching entries (listed by UUID):
Found matching entries (listed by UUID):
5dbf6d1b87e46f0bdf218c42befffd9a77dc678fc6868ee63f97db6145db4625