feat(read): hash_fn attribute

[Fyko]

This PR implements a hash_fn attribute for the fields of a ReadQuery struct.

The way scyllax query coalescing works, the query is Hashed
https://github.com/trufflehq/scyllax/blob/e08edab62b979aee1f0d4af96e31b4cd901e70ea/scyllax/src/executor.rs#L148-L154
and added to a HashMap as the key for other receivers to wait on
https://github.com/trufflehq/scyllax/blob/e08edab62b979aee1f0d4af96e31b4cd901e70ea/scyllax/src/executor.rs#L142

To support column types that are not made by the end user, the hash_fn attribute accepts the value and expects it to be mapped to a value that implements Hash.

For example, the CqlTimestamp type from the scylla library:

#[inline]
fn hash_cql_timestamp(timestamp: &CqlTimestamp) -> i64 {
    timestamp.0
}

#[derive(Debug, Clone, PartialEq, SerializeRow, ReadQuery)]
#[read_query(
    query = r#"select * from "person_by_createdAt" where "createdAt" <= :created_before limit :rowlimit"#,
    return_type = "Vec<super::model::PersonEntity>"
)]
pub struct GetPeopleCreatedBefore {
    #[read_query(coalesce_shard_key, hash_fn = "hash_cql_timestamp")]
    pub created_before: CqlTimestamp,
    pub rowlimit: i32,
}

[codecov]

Codecov Report

Attention: Patch coverage is 52.17391% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 80.59%. Comparing base (e08edab) to head (5c3c218).

Files	Patch %	Lines
example/src/entities/person/queries.rs	0.00%	10 Missing ⚠️
scyllax-macros-core/src/queries/read.rs	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
- Coverage   80.80%   80.59%   -0.22%     
==========================================
  Files          32       32              
  Lines        2422     2437      +15     
==========================================
+ Hits         1957     1964       +7     
- Misses        465      473       +8     

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