Add reply field to Post struct

[doceazedo]

hello! i added the reply field from posts to allow feed generators to filter out replies (or handle them differently). the ReplyRef matches the structure in the atproto post record :-)

[cyypherus]

Thank you for the PR!

I see that the model for post references in atrium also contains cid. I'm wondering if there should be something like a universal "post reference" model in skyfeed.

// From atrium api
#[derive(serde::Serialize, serde::Deserialize, Debug, Clone, PartialEq, Eq)]
#[serde(rename_all = "camelCase")]
pub struct MainData {
    pub cid: crate::types::string::Cid,
    pub uri: String,
}

We already have a post reference sort of model for quoted posts which could use the same type.

#[derive(Debug, Clone)]
pub struct QuoteEmbed {
    pub cid: Cid,
    pub uri: String,
}

What are your thoughts? Is there a chance you'd need the cid? Just considering our options 🤗

[doceazedo]

well, for my use case I only actually need post.reply.is_some()... but since this is a library, others might want to build thread views or fetch the parent post for context... so i would say that ReplyRef is reasonable as it "mirrors" atrium's ReplyRefData.

maybe if someone else needs the CID they can implement some PostRef? :p