use ieee & scopus as databases based on api key availability

[kashyapm94]

If the user has chosen all the databases by default but has no API key for IEEE & Scopus, can we remove these databases automatically before the search begins?

Currently, if all the databases are used, the search function gets the following parameter as input:

databases = ['ACM', 'arXiv', 'bioRxiv', 'IEEE', 'medRxiv', 'PubMed', 'Scopus']

By automatically removing the above-mentioned databases if their API keys are None, the parameter becomes:

databases = ['ACM', 'arXiv', 'bioRxiv', 'medRxiv', 'PubMed']