Add support for Ellipitic Curve w/ brainpool

[TheoGoudout]

There is an AS4 profile called BDEW (cf. https://www.bundesnetzagentur.de/DE/Beschlusskammern/1_GZ/BK6-GZ/2021/BK6-21-282/Mitteilung02/AS4%20Profil.pdf?__blob=publicationFile&v=1) used for the energy market in Germany. This profile requires the usage of Elliptic Curve with brainpoolP256r1 algorithms (ECDSAwithSHA256, etc.) for signing and encrypting.

I've tried to configure Holodeck B2B in order to use my locally generated EC certificates with no luck so far.

Could you please consider adding support for this class of algorithms. If this is already the case, could you please add an example configuration ? I believe some people could be interested in using your application for this purpose.

Thanks