Store school email domains

[PetarSimonovic]

Status

Closes #1325

What's changed?

• Add a school_email_domains table
• Add a SchoolEmailDomain model
• Perform minimal formatting on a domain to strip leading @ and lowercase the string
• Update association on School
• Add and update specs

[Copilot]

Pull request overview

Introduces first-class storage for school email domains by adding a dedicated table/model and wiring it into the School domain model, with accompanying specs.

Changes:

• Added school_email_domains table with a composite unique index per school.
• Added SchoolEmailDomain model with before_validation normalization (strip leading @, downcase).
• Updated School to has_many :school_email_domains and added/updated model specs.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
spec/models/school_spec.rb	Adds association + dependent-destroy coverage for school_email_domains.
spec/models/school_email_domain_spec.rb	Adds model spec coverage for domain normalization behavior.
db/schema.rb	Reflects new school_email_domains table and foreign key.
db/migrate/20260420104937_create_school_email_domains.rb	Creates the new school_email_domains table and composite unique index.
app/models/school_email_domain.rb	Introduces the new model and domain normalization callback.
app/models/school.rb	Adds has_many :school_email_domains, dependent: :destroy.

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[github-actions]

Test coverage

89.5% line coverage reported by SimpleCov.
Run: https://github.com/RaspberryPiFoundation/editor-api/actions/runs/24773204189

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

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[fspeirs]

Overall this looks like the right approach. I have one consideration about validating domains - I feel like it would be helpful to be stricter in checking that the user hasn't typo'ed their domain or misunderstood what we are asking for.

[fspeirs]

Directionally, quite correct. Just some sharpening of the normalisation approach in school_email_domain and a request for a testing method in school.rb. The lack of a testing method is non-blocking if it's coming in a separate PR.

[fspeirs]

Issue: I think this code could be much simpler and doesn't have to expressly handle specific things like uri_host_if_http_url. Instead, I suggest that we just try to parse a URI and, if successful take the host portion:

def normalise_domain
  return if domain.blank?
  value = domain.strip.downcase
  # Add a scheme unless it already has one, so URI can parse it
  value = "http://#{value}" unless value =~ %r{\A[a-z][a-z0-9+\-.]*://}i
  
  uri = URI.parse(value)

  host = uri.host
  return if host.blank?

  if PublicSuffix.valid?(host)
    self.domain = host
  else
    errors.add(:domain, "is not a valid domain")
  end
rescue URI::InvalidURIError
  errors.add(:domain, "is not a valid domain")
end

This is kind of the approach you're taking in uri_host_if_http_url and pulling it up to be the main way we normalise domains: (a) can we parse it with URI::parse and secondly is it a valid suffix.

[fspeirs]

Issue: Callers (including my work) would like a validator method on this called something like: valid_domain?(candidate_domain) which returns true if candidate_domain is registered for this school.

This would allow testing domains presented by registering users without exposing the internal implementation of school_email_domains.