feat: rename crates from gejdr-crud to georm

This commit renames gejdr-crud to georm for an easier name to remember
in case I publish `georm` and `georm-macros`. This commit extracts the
`Georm` (formerly `Crud`) trait from `gejdr-core` to its dedicated
crate `georm` on which gejdr-core now depends.

Currently writing tests

gejdr-core/migrations/20250125193213_macro-test-tables.down.sql

@@ -0,0 +1,5 @@
+DROP TABLE IF EXISTS book_genres;
+DROP TABLE IF EXISTS books;
+DROP TABLE IF EXISTS genres;
+DROP TABLE IF EXISTS authors;
+DROP SCHEMA IF EXISTS tests;

gejdr-core/migrations/20250125193213_macro-test-tables.up.sql

@@ -0,0 +1,26 @@
+CREATE SCHEMA IF NOT EXISTS tests;
+
+CREATE TABLE tests.authors (
+    author_id SERIAL PRIMARY KEY,
+    name VARCHAR(100) NOT NULL
+);
+
+CREATE TABLE tests.books (
+    id SERIAL PRIMARY KEY,
+    title VARCHAR(100) NOT NULL,
+    author_id INT NOT NULL,
+    FOREIGN KEY (author_id) REFERENCES tests.authors(author_id) ON DELETE CASCADE
+);
+
+CREATE TABLE tests.genres (
+    genre_id SERIAL PRIMARY KEY,
+    name VARCHAR(100) NOT NULL
+);
+
+CREATE TABLE tests.book_genres (
+    book_id INT NOT NULL,
+    genre_id INT NOT NULL,
+    PRIMARY KEY (book_id, genre_id),
+    FOREIGN KEY (book_id) REFERENCES tests.books(id) ON DELETE CASCADE,
+    FOREIGN KEY (genre_id) REFERENCES tests.genres(genre_id) ON DELETE CASCADE
+);