Set update interval (1-120 days) manually for NVD API

[oh2fih]

Closes #299

This takes 1-120 days before current date as an integer since it is easier to use than correctly formatted exact datetime.

The NVD API supports downloading data for maximum 120 days. If the period missing CPEs or CVEs is longer than that, full re-population is required.

 - CveXplore.core.nvd_nist.nvd_nist_api - WARNING  - Requested timeframe exceeds the 120 days limit; capping the requested date range to 120 days. End date is now: 2020-08-29T15:40:27.088062
 - CveXplore.core.nvd_nist.nvd_nist_api - INFO     - Getting count for datasource: 2
 - CveXplore.core.nvd_nist.nvd_nist_api - INFO     - urllib3.util.retry did not support configurable backoff_max; falling back to default for urllib3 1.x compatibility
 - CveXplore.core.nvd_nist.nvd_nist_api - ERROR    - Unexpected response type: <Response [404]>
 - CveXplore.core.nvd_nist.nvd_nist_api - ERROR    - Data retrieval error: {'resultsPerPage': 1, 'lastModStartDate': '2020-04-30T15:45:01', 'lastModEndDate': '2020-08-29T15:40:27.088062'}

Usage

>>> from CveXplore import CveXplore
>>> cvx = CveXplore()
>>> cvx.database.update(manual_days=7)
 - CveXplore.core.database_maintenance.main_updater - INFO     - Starting Database update...
 - CveXplore.core.nvd_nist.nvd_nist_api - WARNING  - Could not find a NIST API Key in the environment variable 'NVD_NIST_API_KEY' (e.g. from the '~/.cvexplore/.env' file); you could request one at: https://nvd.nist.gov/developers/request-an-api-key
 - CveXplore.core.database_maintenance.sources_process - INFO     - CPE database update started
 - CveXplore.core.database_maintenance.sources_process - INFO     - Starting download...
 - CveXplore.core.database_maintenance.sources_process - INFO     - Retrieving CPEs starting from 2024-06-25 18:59:04.364340
 - CveXplore.core.nvd_nist.nvd_nist_api - INFO     - Getting count for datasource: 2
 - CveXplore.core.nvd_nist.nvd_nist_api - INFO     - urllib3.util.retry did not support configurable backoff_max; falling back to default for urllib3 1.x compatibility
 - CveXplore.core.database_maintenance.sources_process - INFO     - Preparing to download 2031 CPE entries

Tested with variants:

• cvx.database.update("cpe", 1)
• cvx.database.update("cve", 1)
• cvx.database.update(None, 1)
• cvx.database.update(manual_days=7)
• cvx.database.update(["cve", "via4"], 1)

The last one correctly gives:

 - CveXplore.core.database_maintenance.sources_process - INFO     - Retrieving CVEs starting from 2024-07-01 21:41:33.724703

 - CveXplore.core.database_maintenance.main_updater - WARNING  - Update interval in days not supported by source via4; ignoring