Disabled weak algorithms following Kantara SAML V2.0 Implementation Profile

[peppelinux]

Kantara SAML V2.0 Implementation Profile for Federation Interoperability specifications:

[IIP-ALG08]
Implementations MUST support the ability to prevent the use of particular algorithms such that any attempt to configure or select them will result in failure. The set of such algorithms MUST be configurable and it is RECOMMENDED that the default set include:

Digest

http://www.w3.org/2001/04/xmldsig-more#md5 [RFC4051]

Signature

http://www.w3.org/2001/04/xmldsig-more#rsa-md5 [RFC4051]

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[c00kiemon5ter]

As the spec says, this must be configurable. It is a policy setting, not something we must disable. I someone needs to, they can and should be able to use any weak algorithm.

This will be done as it has been discussed in #421

[peppelinux]

Ok Ivan, I'll do a PR with this feature