Add support for importing stringified JSON

[lthievenaz-keeper]

The JSON import command requires a physical file holding sensitive data:

• JSON
• ZIP

Added support for passing stringified JSON as the filename, which will import the data without needing to store it in a file. This improves security, SDK use-cases, integrations with ephemeral storage.

Example command syntax:

CLI

import --format json "[{\"title\":\"JSON record title\",\"login\":\"example_login\"}]"

SDK

from keepercommander.importer.imp_exp import _import

data = json.dumps(list_records)
_import(params, 'json', data)

[lthievenaz-keeper]

Closing, pushed into master instead of release