Bump cdav-library from `e12e386` to `8bb1396`

Bumps [cdav-library](https://github.com/nextcloud/cdav-library) from `e12e386` to `8bb1396`.
- [Release notes](https://github.com/nextcloud/cdav-library/releases)
- [Commits](https://github.com/nextcloud/cdav-library/compare/e12e386576268007a38744cc10d9c4361d6367e7...8bb139608ae4610efebec7dded1627e8f9ba2731

)

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