feat: adding basic support for tables (#19)

Start by adding support for table flattening and max depth, based on [table_tests.go](https://github.com/cloudquery/plugin-sdk/blob/main/schema/table_test.go)

Author: mnorbury

Diff for: lib/src/main/java/io/cloudquery/schema/Table.java

@@ -0,0 +1,44 @@
+package io.cloudquery.schema;
+
+import lombok.Builder;
+import lombok.Getter;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@Builder(toBuilder = true)
+@Getter
+public class Table {
+    public static List<Table> flattenTables(List<Table> tables) {
+        Map<String, Table> flattenMap = new HashMap<>();
+        for (Table table : tables) {
+            Table newTable = table.toBuilder().relations(Collections.emptyList()).build();
+            flattenMap.put(newTable.name, newTable);
+            for (Table child : flattenTables(table.getRelations())) {
+                flattenMap.put(child.name, child);
+            }
+        }
+        return flattenMap.values().stream().toList();
+    }
+
+    public static int maxDepth(List<Table> tables) {
+        int depth = 0;
+        if (tables.isEmpty()) {
+            return 0;
+        }
+        for (Table table : tables) {
+            int newDepth = 1 + maxDepth(table.getRelations());
+            if (newDepth > depth) {
+                depth = newDepth;
+            }
+        }
+        return depth;
+    }
+
+    private String name;
+
+    @Builder.Default
+    private List<Table> relations = Collections.emptyList();
+}

Diff for: lib/src/test/java/io/cloudquery/schema/TableTest.java

@@ -0,0 +1,52 @@
+package io.cloudquery.schema;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class TableTest {
+
+    public Table testTable;
+
+    @Before
+    public void setUp() {
+        testTable = Table.builder().
+                name("test").
+                relations(List.of(
+                        Table.builder().name("test2").build(),
+                        Table.builder().name("test3").build(),
+                        Table.builder().name("test4").build()
+                )).build();
+    }
+
+    @Test
+    public void shouldFlattenTables() {
+        List<Table> srcTables = List.of(testTable);
+        List<Table> flattenedTables = Table.flattenTables(srcTables);
+
+        assertEquals(1, srcTables.size());
+        assertEquals(3, testTable.getRelations().size());
+        assertEquals(4, flattenedTables.size());
+    }
+
+    @Test
+    public void shouldFlattenTablesWithDuplicates() {
+        List<Table> srcTables = List.of(testTable, testTable, testTable);
+        List<Table> flattenedTables = Table.flattenTables(srcTables);
+
+        assertEquals(3, srcTables.size());
+        assertEquals(3, testTable.getRelations().size());
+        assertEquals(4, flattenedTables.size());
+    }
+
+    @Test
+    public void shouldReturnMaxDepth() {
+        assertEquals(0, Table.maxDepth(Collections.emptyList()));
+        assertEquals(2, Table.maxDepth(List.of(testTable)));
+        assertEquals(3, Table.maxDepth(List.of(testTable.toBuilder().relations(List.of(testTable)).build())));
+    }
+}