v0.6.2 — document DCR TTL + signing secret in mtaext example

What's changed since v0.6.1

• docs(mtaext): document OAuth DCR settings in mta-overrides.mtaext.example:
  • SAP_OAUTH_DCR_TTL_SECONDS (0 = registrations never expire) — safe to keep in the descriptor.
  • How to set the DCR signing secret out-of-band: LISA_DCR_SIGNING_SECRET is a secret and must be set via cf set-env (not the mtaext), otherwise it falls back to the XSUAA clientsecret which cf deploy rotates, invalidating cached client registrations.

No runtime/behavior changes.

Full changelog: v0.6.1...v0.6.2