Feature: Not found message by context

[syphax-bouazzouni]

What

This PR make error messages more descripitf, for the case of Onotology not found , Class not found and Onotology no roots found errors

Before

Missing roots error

Onotology not found error

Class not found

After

Missing roots error

Onotology not found error

Class not found

[jonquet]

This is a first patch for a deeper refactoring of the exceptions handling on the front end. Ultimately the idea is to avoid the "Something went wrong" screen for things that are trivial to inform the user.

[jvendetti]

Hi Syphax & Clement. If you guys are looking at refactoring the error pages and descriptions, I have some comments for your consideration.

I think it would be nice to uniformly use "not found" for 404 errors. In other words, instead of "missing" for classes and "not found" for ontologies, it seems cleaner to use "not found" for both.

Also, using the full class ID in the class not found error doesn't look that user-friendly to me. I think it would be nicer to use the preferred label. You could add the class ID below - perhaps using a smaller text in a greyed out color.

I'm imagining something similar to Google's 404 pages:

404. Class not found error.
The requested class 'accident reporting' was not found in AGROVOC.

Class ID: http://aims.fao.org/aos/agrovoc/c_331462

I understand the above is problematic if there's no preferred label, but I'm just thinking out loud here.

Possible equivalent for ontologies:

404. Ontology not found error.
The requested ontology 'Animal Trait Ontology for Livestock' was not found in AgroPortal.

Ontology ID: ATOL

With regard to the "missing roots" error - this feels like a developer-centric error message that I would expect to see in a log file as the underlying cause of why the Rails application was unable to display a class tree. It's immediately evident to me what it means, but I don't think it means anything to an end user. I'm having a hard time thinking of a good alternative mesage - perhaps something like "Unable to load the class tree for OMO".

It's kind of unfortunate that missing roots results in different presentations of an error depending on what URL pattern is used. This URL (https://bioportal.bioontology.org/ontologies/OMO/?p=classes) results in the main 404 page:

... and this URL (https://bioportal.bioontology.org/ontologies/OMO/?p=classes&conceptid=root) results in the Classes tab with an error description:

[jonquet]

@jvendetti Thanks for remarks. We have not discuss this again with @syphax-bouazzouni but will do. Bye.