Tests? 🙃

Only option 2 makes sense to me. If you need your enum to have a canonical scalar representation, you should use a backed enum (that's what they are about).

• it would detect changes such as exchanging values of 2 enum cases

that's not something we need to detect IMO (your DB would also have issues in such case, and this would require an insane architecture IMO)

Alright then, thanks for your input, @stof.
@derrabus I'll add tests for the signature hasher, I was actually surprised to find none.

@chalasr @derrabus @stof Ready for review.

I've split the PR into 3 commits:

• Commit 1 adds the feature, and adds missing tests for SignatureHasher.
  As you can see, tests are rather ugly as in its current state, SignatureHasher uses a hardcoded combination of hash_*() functions, base64_encode() and strtr(), with no mechanism in place to mock these:

  ['someValue', ['arbitraryValue'], 'kfMzZgYYD1oeqSSW7m0k94VuRvS7LeHcKq-PKU8WD7k~0nuV8X2IlHqxDdPRNOLP-wp_v2KdVL9dNYJ0_557fGc~'],
  ['someValue', ['identifier', 'arbitraryValue'], 'myxvvho8WkMuOcMMeuRlZQFe58TNDQFgDrVFb8SZ50g~iJ4d_Agaa0AaCHZinVr_zZCgR2nSZgokvXIkv7ne1b4~'],

• Commit 2 proposes introducing HasherInterface and HashContextInterface, which are now mockable, and allow to see what is hashed exactly in tests:

  - ['someValue', ['arbitraryValue'], 'kfMzZgYYD1oeqSSW7m0k94VuRvS7LeHcKq-PKU8WD7k~0nuV8X2IlHqxDdPRNOLP-wp_v2KdVL9dNYJ0_557fGc~'],
  - ['someValue', ['identifier', 'arbitraryValue'], 'myxvvho8WkMuOcMMeuRlZQFe58TNDQFgDrVFb8SZ50g~iJ4d_Agaa0AaCHZinVr_zZCgR2nSZgokvXIkv7ne1b4~'],
  + ['someValue', ['arbitraryValue'], true, 'HMAC(HASH(:someValue):1234567890:username,s3cr3t)HASH(:someValue)'],
  + ['someValue', ['identifier', 'arbitraryValue'], true, 'HMAC(HASH(:username:someValue):1234567890:username,s3cr3t)HASH(:username:someValue)'],

• Commit 3 fixes a missing dependency on symfony/property-access, highlighted by the newly added tests for SignatureHasher.