Refactor CPE imports and add NVDCPEHandler for JSON feeds

[oh2fih]

This PR refactors the legacy CPE dictionary import logic to be more extendable and adds support for the new NVD CPE Dictionary 2.0 JSON feeds.

• Refactor legacy XML CPE imports
  • Introduced abstract base class CPEImportHandler.
  • Added XMLCPEHandler for legacy XML parsing.
  • Added CPEDownloader for downloading and uncompressing CPE dictionaries.
• Support for NVD CPE Dictionary 2.0 JSON
  • Added NVDCPEHandler to handle the new JSON format.
  • Supports:
    • Tar archives containing multiple JSON files (current standard).
    • Single JSON files (for flexibility).
  • Deprecated CPEs are skipped to reduce false positives (a behavior not present in XML import).
  • Logs each JSON file inside tar archives for easier debugging.
  • Add an example of the new format in README.md.
• Updates to import logic (import.py)
  • Import logic moved into the library for cleaner structure and reuse.
  • File-type detection based on extension; wrong content types will raise exceptions.
  • Simplified CLI flags:
    • Removed redundant --update.
    • Converted toggle flag --download to boolean.
• Configuration
  • Default configuration updated to use CPE Dictionary 2.0 feed.
  • Fix inconsistency between default configuration and documentation (in favor of documentation).

Resolves #18

[oh2fih]

Testing legacy XMLCPEHandler (existing file only)

cpe:
  path: './data/official-cpe-dictionary_v2.3.xml'
  source: 'https://nvd.nist.gov/feeds/xml/cpe/dictionary/official-cpe-dictionary_v2.3.xml.gz'

$ python3 ./bin/import.py --replace
Using existing file ./data/official-cpe-dictionary_v2.3.xml ...
Flushing 165859 keys from the database...
Populating the database (please be patient)...
Using XMLCPEHandler to parse file ./data/official-cpe-dictionary_v2.3.xml...
... 5000 items processed (13519 words) in 2 seconds
. . .
... 1455000 items processed (4337016 words) in 686 seconds
Finished XMLCPEHandler[official-cpe-dictionary_v2.3.xml]: 1456315 items (4341134 words) in 687 seconds.
Done! 166263 keys inserted.

Testing new NVDCPEHandler together with CPEDownloader

cpe:
  path: './data/nvdcpe-2.0.tar'
  source: 'https://nvd.nist.gov/feeds/json/cpe/2.0/nvdcpe-2.0.tar.gz'

$ python3 ./bin/import.py --replace --download
Downloading CPE data from https://nvd.nist.gov/feeds/json/cpe/2.0/nvdcpe-2.0.tar.gz ...
Uncompressing ./data/nvdcpe-2.0.tar.gz ...
Flushing 166263 keys from the database...
Populating the database (please be patient)...
Using NVDCPEHandler to parse file ./data/nvdcpe-2.0.tar...
NVDCPEHandler parsing nvdcpe-2.0-chunks/nvdcpe-2.0-chunk-00001.json...
... 5000 items processed (14121 words) in 3 seconds
. . .
NVDCPEHandler parsing nvdcpe-2.0-chunks/nvdcpe-2.0-chunk-00014.json...
... 1345000 items processed (4009090 words) in 653 seconds
... 1350000 items processed (4023734 words) in 656 seconds
... 1355000 items processed (4040000 words) in 659 seconds
... 1360000 items processed (4054575 words) in 661 seconds
... 1365000 items processed (4068814 words) in 662 seconds
... 1370000 items processed (4082728 words) in 664 seconds
... 1375000 items processed (4095072 words) in 666 seconds
... 1380000 items processed (4109651 words) in 669 seconds
Finished NVDCPEHandler[nvdcpe-2.0.tar]: 1382942 items (4115900 words), 86664 skipped in 670 seconds.
Done! 165859 keys inserted.

$ python3 ./bin/import.py --replace
Using existing file ./data/nvdcpe-2.0.tar ...
Flushing 165859 keys from the database...
Populating the database (please be patient)...
Using NVDCPEHandler to parse file ./data/nvdcpe-2.0.tar...
NVDCPEHandler parsing nvdcpe-2.0-chunks/nvdcpe-2.0-chunk-00001.json...
... 5000 items processed (14121 words) in 4 seconds
. . .
... 1380000 items processed (4109651 words) in 676 seconds
Finished NVDCPEHandler[nvdcpe-2.0.tar]: 1382942 items (4115900 words), 86664 skipped in 677 seconds.
Done! 165859 keys inserted.

Lookup after JSON import

$ python3 lookup.py microsoft teams | jq .
[
  [
    118171,
    "cpe:2.3:a:microsoft:teams"
  ],
  [
    113340,
    "cpe:2.3:o:hp:elite_slice_g2_-_partner_ready_with_microsoft_teams_rooms_firmware"
  ],
  [
    111235,
    "cpe:2.3:h:hp:elite_slice_g2_-_partner_ready_with_microsoft_teams_rooms"
  ],
  [
    108091,
    "cpe:2.3:o:hp:elite_slice_g2_with_microsoft_teams_rooms_firmware"
  ],
  [
    103192,
    "cpe:2.3:h:hp:elite_slice_g2_with_microsoft_teams_rooms"
  ]
]

[adulau]

Awesome! I'll do some tests and merge it if everything is fine. Thanks a lot. That's a great contribution.