Atproto, serde deserialize & move strong_ref

This adds Serde deserialization. It also needs to add an error for
handling the failure on these deserializations.

I broke strong_ref into its own file because it was starting to grow a
lot.

atproto/src/error.rs

@@ -20,6 +20,8 @@ pub enum FormatError {
 pub enum ParseError {
   #[error("Time Parse Error: {0}")]
   Datetime(#[from] time::error::Parse),
+  #[error("Json Parse Error: {0}")]
+  Serde(#[from] serde_json::error::Error),
   #[error("Length of parsed object too long, max: {max:?}, got: {got:?}.")]
   Length { max: usize, got: usize },
   #[error("Currently Did is enforced, cannot use handle, {handle:?}")]