Add metas to PartiQL Common (#488)

Adds an implementation for storing metadata for PartiQL objects. Currently, the implementation does not include any traits. It introduces `PartiqlMetadata` and `PartiqlMetaValue` structures:

```rust
        let foo_val = PartiqlMetaValue::String("foo".to_string());
        let i64_val = PartiqlMetaValue::Int64(2);

        let expected_vec_val = vec![foo_val, i64_val];
        let expected_bool_val = true;
        let expected_int_val = 2;
        let expected_float_val = 2.5;
        let expected_str_val = "foo";

        let mut expected_map = PartiqlMetadata::new();
        expected_map.insert("bool value", expected_bool_val.into());
        expected_map.insert("integer value", expected_int_val.into());

        let mut metas = PartiqlMetadata::new();
        metas.insert("vec value", expected_vec_val.clone().into());
        metas.insert("bool value", expected_bool_val.into());
        metas.insert("integer value", expected_int_val.into());
        metas.insert("float value", expected_float_val.into());
        metas.insert("string value", expected_str_val.into());
        metas.insert("map value", expected_map.clone().into());

        let vec_val = metas.vec_value("vec value").expect("vec meta value");
        let bool_val = metas.bool_value("bool value").expect("bool meta value");
        let int_val = metas.i32_value("integer value").expect("i32 meta value");
        let float_val = metas.f64_value("float value").expect("f64 meta value");
        let string_val = metas.string_value("string value").expect("string meta value");
        let map_val = metas.map_value("map value").expect("map meta value");

        assert_eq!(vec_val, expected_vec_val.clone());
        assert_eq!(bool_val, expected_bool_val.clone());
        assert_eq!(int_val, expected_int_val.clone());
        assert_eq!(float_val, expected_float_val.clone());
        assert_eq!(string_val, expected_str_val);
        assert_eq!(map_val, expected_map.clone());
```

CHANGELOG.md

@@ -9,12 +9,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - partiql-ast: fixed pretty-printing of `PIVOT`
 - partiql-ast: improved pretty-printing of `CASE` and various clauses
-- 
+
 ### Added
 - Added `partiql-common`.
 - Added `NodeId` to `StaticType`.
 - *BREAKING* Added thread-safe `PartiqlShapeBuilder` and automatic `NodeId` generation for the `StaticType`.
 - Added a static thread safe `shape_builder` function that provides a convenient way for using `PartiqlShapeBuilder` for creating new shapes.
+- Added `partiql_common::meta::PartiqlMetadata`
 
 ### Removed
 - *BREAKING* Removed `partiql-source-map`.

partiql-common/Cargo.toml

@@ -23,6 +23,7 @@ bench = false
 indexmap = "2.2"
 pretty = "0.12"
 serde = { version = "1.*", features = ["derive"], optional = true }
+rust_decimal = { version = "1.25.0", default-features = false, features = ["std"] }
 smallvec = { version = "1.*" }
 thiserror = "1.0"
 

partiql-common/src/lib.rs

@@ -1,4 +1,5 @@
 #![deny(rust_2018_idioms)]
 #![deny(clippy::all)]
+pub mod metadata;
 pub mod node;
 pub mod syntax;