fix: changed base location for graph_from_graphdb and added tests

[schochastics]

Fix #1712
Downloaded the database from here: https://zenodo.org/records/11204020
and hosted it here: https://github.com/schochastics/graphsdb/

General question: should we host it somewhere else?

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[maelle]

good idea!

I see a typo in the file "algothitms", it could be fixed at the same time.

I wonder whether the database should be cached in an user dir. Should the argument of where to save it be exposed?

[szhorvat]

and hosted it here: https://github.com/schochastics/graphsdb/

I suggest hosting it under the igraph organization for the purposes of allowing the function to work.

In our own copy, we should mention the license and list the original authors, in addition to linking to Zenodo. I'm really glads to see that this is on Zenodo given that the MIVIA website is gone now.

@maelle

Would we be allowed to store a copy in https://github.com/igraph/igraphdata?

This dataset is way too large for the igraphdata package. I suggest using a separate repo, exactly what @schochastics did, but under the igraph organization. I believe you should be able to create a new repo, but if not let me know and I'll see if I can fix that.

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Can this function operate with a local copy of the database? Would this be easy to implement, and if yes, can we include an explanation of how to do it? file:/// URL in base?

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Other than the comments above, this LGTM.

[schochastics]

I will try to host it under the igraph org and put all the necessary information into the README. The files have a CC license so that should all be fine. I also checked that it works with a local copy. You simply need to provide the path to the database. I will also update the docs so that this is clear

[krlmlr]

Do these actually work and look better? Please merge when good and green.