Feature: Add portal configuration model reading from config file

[syphax-bouazzouni]

fix agroportal/project-management#592, by adding a model to define the portal configuration, containing the following attributes:

      model :SemanticArtefactCatalogue, namespace: :mod, name_with: :acronym
      attribute :acronym, enforce: [:unique, :existence]
      attribute :title, namespace: :dcterms, enforce: [:existence]
      attribute :color, enforce: [:existence, :valid_hash_code]
      attribute :description, namespace: :dcterms
      attribute :logo, namespace: :foaf, enforce: [:url]
      attribute :numberOfArtefacts, namespace: :mod, handler: :ontologies_count
      attribute :federated_portals
      attribute :fundedBy, enforce: [:list] 

the model is not saved in the triple store, but use the configuration files, to fill its attributes.

    config.ui_name                       = 'Bioportal'
    config.title                         = 'NCBO BioPortal'
    config.description                   = "The world's most comprehensive repository of biomedical ontologies "
    config.color                         = '#234979'
    config.logo                          = ''
    config.fundedBy                      = [
        {
          img_src: 'https://identity.stanford.edu/wp-content/uploads/sites/3/2020/07/block-s-right.png',
          url: 'https://www.stanford.edu',

        },
        {
          img_src: 'https://ontoportal.org/images/logo.png',
          url: 'https://ontoportal.org/',
        }
    ]
    config.federated_portals = {
          'agroportal' => {
            api: 'http://data.agroportal.lirmm.fr',
            ui: 'http://agroportal.lirmm.fr',
            apikey: 'XXXX',
            color: '#1e2251'
          },
          'bioportal' => {
                  api: 'http://data.bioontology.org',
                  ui: 'http://bioportal.bioontology.org',
                  apikey: 'XXXX',
                  color: '#234979'
           },

    }

[codecov]

Codecov Report

Attention: Patch coverage is 87.09677% with 4 lines in your changes missing coverage. Please review.

Project coverage is 81.90%. Comparing base (337dce9) to head (560783f).
Report is 19 commits behind head on development.

Files with missing lines	Patch %	Lines
lib/ontologies_linked_data/models/portal_config.rb	87.09%	4 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #155      +/-   ##
===============================================
+ Coverage        81.31%   81.90%   +0.59%     
===============================================
  Files               89      101      +12     
  Lines             6512     6666     +154     
===============================================
+ Hits              5295     5460     +165     
+ Misses            1217     1206      -11     

Flag	Coverage Δ
unittests	81.90% <87.09%> (+0.59%)	⬆️

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