feat(mysql): add support for vector indices (#139)

* feat(mysql): add support for vector indices

PlanetScale recently added vector support to their fork of mysql.
If a vector index is added to it, then sea-orm generate entity command
panics because the index type is not recognized by its parser.

This PR adds support for recognizing vector indices as a valid index
type.

Test Plan: Created a planet scale database with a vector index, and ran
`generate entity` command. Verified that after this change, the command
no longer crashes and creates valid files.

* gate behind planetscale feature flag

Cargo.toml

@@ -53,6 +53,7 @@ discovery = ["futures", "parser"]
 parser = ["query"]
 query = ["def"]
 writer = ["def"]
+planetscale = []
 probe = ["query"]
 sqlx-dep = ["sqlx"]
 sqlx-all = ["sqlx-mysql", "sqlx-postgres", "sqlx-sqlite"]

src/mysql/def/index.rs

@@ -54,4 +54,7 @@ pub enum IndexType {
     RTree,
     #[iden = "SPATIAL"]
     Spatial,
+    #[cfg(feature = "planetscale")]
+    #[iden = "VECTOR"]
+    Vector,
 }

src/mysql/writer/index.rs

@@ -52,6 +52,12 @@ impl IndexInfo {
                     self.idx_type.to_string(),
                 ))));
             }
+            #[cfg(feature = "planetscale")]
+            IndexType::Vector => {
+                index.index_type(sea_query::IndexType::Custom(SeaRc::new(Alias::new(
+                    self.idx_type.to_string(),
+                ))));
+            }
         }
         index
     }