feat: move termix identity into a plugin (C6)

plugins/termix-identity/CHANGELOG.md

@@ -0,0 +1,14 @@
+# Changelog
+
+## 1.0.0
+
+Bundled with Termix 2.9.0.
+
+- Termix ID moved out of core. The resolver is now
+  `/plugin-api/termix-identity/u/<handle>`; the 2.8 URLs under
+  `/termix-id/u/` redirect to it.
+- Handles, published keys and certificate authorities are kept on upgrade.
+  The CA private key is now encrypted with the installation key instead of
+  the owner's data key, so issuing a certificate no longer needs the data
+  key unlocked.
+- New `termix-identity.use` permission, granted to admins and users.