Handle all types of ACS endpoint specifications

[peppelinux]

With these changes a SP ACS service configured with a 3-tuple (URL, binding, index) works correctly.

Fixes #599

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[peppelinux]

TODO:
a unit test

[c00kiemon5ter]

I think this is correct.
We do handle indexes in https://github.com/IdentityPython/pysaml2/blob/2641019/src/saml2/metadata.py#L405-L410
In Config.endpoint we do not care about the index, so we should ignore that part of the tuple.

[peppelinux]

I think this is correct.
We do handle indexes in https://github.com/IdentityPython/pysaml2/blob/2641019/src/saml2/metadata.py#L405-L410
In Config.endpoint we do not care about the index, so we should ignore that part of the tuple.

I agree, and looking at that code ... Hundreds of nested if statements in a generic try/except... In a for loop. We'll die crazy...

That function could be entirely refactored.
We could use .get method, no more try with all those "haduken" codes!

[peppelinux]

And not at last, we shouldn't return sometimes a string and sometimes a tuple. Let's return a tuple and anything else ...

Let's refactor that function, it's too noisy

[peppelinux]

@c00kiemon5ter you approved this, is it time to merge or do we have to put in also the unit test, before?