Annotated the query with the federation partners

[JervenBolleman]

Use the ontology created in the ontology branch to annotate that a query federates with certain endpoints.
Tests that the query service clauses match the annotations are also added.

[vemonet]

There is some issue with Bgee virtuoso which makes services calls to https://www.bgee.org/sparql fail, the ending slash is required for it to work (in SERVICE calls only...), I have added it

And Ensembl xrefs between uniprot and bgee needs a small rewrite to work (uniprot ensembl IRIs use version number in IRIs, while bgee does not)

[vemonet]

Wouldn't it better to use spex:federatesWith instead of sparql-examples:federates_with for the predicate? Camecase is usually more commonly used for predicates than snakecase

For the prefix maybe a shorthand like spex: or rqex:? Having - in the left part of a CURIE is authorized but some coloration systems are not working well with it

[JervenBolleman]

@vemonet spex:federatesWith could you give me a link to the ontology file please

[vemonet]

The ontology was pushed in a different PR: #22

I can make some improvements to the ontology, should I push it back to this PR 22 or this one?

[JervenBolleman]

I was thinking you where referring to an ontology associated with zazuko spex.
Yes using camelcase is fine I will fix it.

[vemonet]

Ah no, I was thinking just changing the prefix since https://prefix.cc/spex was not matching anything