chore: rename git_auth to external_auth in our schema (#9935)

* chore: rename `git_auth` to `external_auth` in our schema

We're changing Git auth to be external auth. It will support
any OAuth2 or OIDC provider.

To split up the larger change I want to contribute the schema
changes first, and I'll add the feature itself in another PR.

* Fix names

* Fix outdated view

* Rename some additional places

* Fix sort order

* Fix template versions auth route

* Fix types

* Fix dbauthz

coderd/database/migrations/000158_external_auth.up.sql

@@ -0,0 +1,25 @@
+BEGIN;
+
+ALTER TABLE template_versions RENAME COLUMN git_auth_providers TO external_auth_providers;
+
+ALTER TABLE git_auth_links RENAME TO external_auth_links;
+
+DROP VIEW template_version_with_user;
+-- If you need to update this view, put 'DROP VIEW template_version_with_user;' before this.
+CREATE VIEW
+	template_version_with_user
+AS
+SELECT
+	template_versions.*,
+	coalesce(visible_users.avatar_url, '') AS created_by_avatar_url,
+	coalesce(visible_users.username, '') AS created_by_username
+FROM
+	template_versions
+	LEFT JOIN
+		visible_users
+	ON
+		template_versions.created_by = visible_users.id;
+
+COMMENT ON VIEW template_version_with_user IS 'Joins in the username + avatar url of the created by user.';
+
+COMMIT;