add initial space logic/behaviour

internal/db/migrations/00005_create_spaces_tables.sql

@@ -0,0 +1,32 @@
+-- +goose Up
+-- +goose StatementBegin
+CREATE TABLE IF NOT EXISTS spaces (
+    id TEXT PRIMARY KEY NOT NULL,
+    name TEXT NOT NULL,
+    owner_id TEXT NOT NULL,
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (owner_id) REFERENCES users(id) ON DELETE CASCADE
+);
+
+CREATE TABLE IF NOT EXISTS space_members (
+    space_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    role TEXT NOT NULL CHECK (role IN ('owner', 'member')),
+    joined_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    PRIMARY KEY (space_id, user_id),
+    FOREIGN KEY (space_id) REFERENCES spaces(id) ON DELETE CASCADE,
+    FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
+);
+
+CREATE INDEX IF NOT EXISTS idx_spaces_owner ON spaces(owner_id);
+CREATE INDEX IF NOT EXISTS idx_space_members_user ON space_members(user_id);
+-- +goose StatementEnd
+
+-- +goose Down
+-- +goose StatementBegin
+DROP INDEX IF EXISTS idx_space_members_user;
+DROP INDEX IF EXISTS idx_spaces_owner;
+DROP TABLE IF EXISTS space_members;
+DROP TABLE IF EXISTS spaces;
+-- +goose StatementEnd