[FEATURE] Consider to use NIP-32

[atrifat]

Issue

Consider to use NIP-32 instead of current implementation using kind 9978. We need to transform data format properly and learn how to apply it based on NIP-32.

Solution

Implementation Status:

• NIP-32 support for NSFW Classification (Content-safety). Closed with Feat NIP-32 Content-safety Compatibility Support  #36 .
• NIP-32 support for Language Classification. Closed with Feat NIP-32 Language Compatibility Support #37 .
• NIP-32 support for Hate speech Classification (Toxicity). Closed with Feat NIP-32 Toxicity Compatibility Support #38 .
• NIP-32 support for Sentiment Classification. Closed with Feat NIP-32 Sentiment Compatibility Support #39 .
• NIP-32 support for Topic Classification. Closed with Feat NIP-32 Topic Classification Compatibility Support #40 .

Implementation related to atrifat/nostr-filter-relay#18 .