split store and store_sqlite implementatio into multiple crates

crates/store_sqlite/migrations/1_init.sql

@@ -0,0 +1,37 @@
+CREATE TABLE calendars (
+    principal TEXT NOT NULL,
+    id TEXT NOT NULL,
+    synctoken INTEGER DEFAULT 0 NOT NULL,
+    displayname TEXT,
+    description TEXT,
+    "order" INT DEFAULT 0 NOT NULL,
+    color TEXT,
+    timezone TEXT NOT NULL,
+    deleted_at DATETIME,
+    PRIMARY KEY (principal, id)
+);
+
+CREATE TABLE calendarobjects (
+    principal TEXT NOT NULL,
+    cal_id TEXT NOT NULL,
+    id TEXT NOT NULL,
+    ics TEXT NOT NULL,
+    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    deleted_at DATETIME,
+    PRIMARY KEY (principal, cal_id, id),
+    FOREIGN KEY (principal, cal_id)
+    REFERENCES calendars (principal, id) ON DELETE CASCADE
+);
+
+CREATE TABLE calendarobjectchangelog (
+    -- The actual sync token is the SQLite field 'ROWID'
+    principal TEXT NOT NULL,
+    cal_id TEXT NOT NULL,
+    object_id TEXT NOT NULL,
+    operation INTEGER NOT NULL,
+    synctoken INTEGER DEFAULT 0 NOT NULL,
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    PRIMARY KEY (principal, cal_id, created_at),
+    FOREIGN KEY (principal, cal_id)
+    REFERENCES calendars (principal, id) ON DELETE CASCADE
+);