Add reference to resources

[oriolgual]

This is a Feature Proposal

🎩 Description

Users and admins need an easy way to refer to a unique resource (proposal, meeting, result, etc) in a friendly way (without having to know the ID). This could be useful when linking resources or just referring to them.

We need to add a method so that every resource has its unique reference, it could be something like this:

BCN-DPP-2017-02-6589 which translates to:

• BCN: A setting configured at the organization to be prepended to each reference.
• DPP: Unique name identifier for a resource: Decidim::Proposals::Proposal (DMM for meetings or DBP for projects).
• 2017-02: Year-Month of the resource creation date
• 6589: ID of the resource

After this, users should be able to see the reference in proposals, meetings, results and projects.

📌 Related issues

• Better experience when linking resources #950

📋 Additional Data

• https://decidim-design.herokuapp.com/proposal-view/
• Screenshot:
  
• Use the Resourceable concern and ResourceManifest to implement this.

[mrcasals]

The DPP part can be non-unique in some installations and it might be weird. What about taking the first 4 letters of the resource name? Meeting => MEET, Projects => PROJ, Proposals => PROP.

Also, I'm thinking about external resources. In L'Hospitalet installation, custom resources will be scoped in DecidimHospitalet::EngineName::ResourceName, so whoever implements this needs to take this capitalization into account with the model @oriolgual suggested.

[oriolgual]

@mrcasals we delegate this to the ResourceManifest and when you register a new resource it gets validated that it's unique. Ok with the 4 letter approach.