Upgrade to ProtonMail/go-crypto v3 API

See merge request !147

In passing, also update go:build tags for integration tests.

Update module github.com/go-ldap/ldap/v3 to v3.4.10

See merge request !141

Update module golang.org/x/net to v0.34.0

See merge request !144

Update git.autistici.org/id/auth digest to 7ed6705

See merge request !146

The CI test runner tends to run out of memory, resulting in
flaky tests.

Update module golang.org/x/crypto to v0.32.0

See merge request !143

Update git.autistici.org/ai3/go-common digest to 62b40ad

See merge request !145

Update module golang.org/x/net to v0.33.0

See merge request !140

Refactor validation code for readability

Closes #11 and #20

See merge request !142

This reverts commit 982b2c7d.

Also make ValidationError just a simple error type with an associated
field name, which is a lot easier to reason about.

Rely on standard errors.Join() semantics for error containerization,
and instead implement a nicer ErrorToJSON() method that relies on
error inspection.

Improve compliance of our response error chain to the Go error
interface, so that now we can use errors.Is() and such to test for our
error class wrappers.

The validation code is very complex but it includes sub-components
that can be meaningfully isolated. Split those into separate files.

Update git.autistici.org/ai3/tools/aux-db digest to 00555b7

See merge request !136

Update git.autistici.org/id/go-sso digest to 0e26b5e

See merge request !134

Update module github.com/prometheus/client_golang to v1.20.5

See merge request !127

Update git.autistici.org/id/auth digest to 7381201

See merge request !133

Update git.autistici.org/ai3/go-common digest to 880a2c5

See merge request !132

Update git.autistici.org/id/usermetadb digest to b5c24a0

See merge request !135