feat: one-to-many relation helper

Allow one to specify that a field of a model is a foreign key.
It will generate a bunch of helper methods to query related entities
from one entity.

lib/sqlxgentools_cli/src/generators/mod.rs

@@ -0,0 +1,20 @@
+use fully_pub::fully_pub;
+use serde::Serialize;
+
+pub mod migrations;
+pub mod repositories;
+
+#[derive(Serialize, Debug)]
+#[fully_pub]
+enum SourceNode {
+    File(String),
+    Directory(Vec<SourceNodeContainer>)
+}
+
+#[derive(Serialize, Debug)]
+#[fully_pub]
+struct SourceNodeContainer {
+    name: String,
+    inner: SourceNode
+}
+