Consolidate connector provider dispatch behind a typed *Registry

The console previously dispatched per-provider logic through a fan of
init()-side-effect maps (driver names, OAuth2 metadata, probe URLs,
display names, settings switches), spread across pkg/connector,
pkg/accessreview/drivers and the console v1 resolvers. Adding a new
provider required edits in every one of those places and a corresponding
switch arm in CreateConnectorRequest. The same per-provider knowledge
also leaked into Helm templates as hand-rolled environment-variable
blocks per connector.

This commit collapses the dispatch surface into a single typed
*provider.Registry. The registry is constructed once by
NewBuiltinRegistry at probod startup and threaded as an explicit
dependency into every consumer (accessreview service, console v1
resolver, OAuth2 wiring). There is no package-level state. Each
provider lives in one file under pkg/connector/provider/ that exposes
a private xxxRegistration() *Registration constructor; NewBuiltinRegistry
enumerates them.

CreateConnectorRequest loses its per-provider settings fields and
takes a single RawSettings json.RawMessage produced by the
per-provider MarshalSettings closure. The 1Password SCIM bridge URL
is validated at create time (http(s) scheme + non-empty host) so a
malformed value fails fast at the resolver boundary. The Helm chart
gains probo.connectorEnv and probo.connectorSecretEntries templates
so adding a connector requires zero Helm changes. Access-review name
resolution moves into the same Registration value to keep one
authoritative dispatch table.

Tests cover every Registration (DisplayName, NewDriver wired),
Register error paths (nil, empty Provider, empty DisplayName,
duplicate), All / ProviderDisplayName / ProviderOAuth2Scopes /
ProbeURL hit and miss paths, the ApplyOAuth2Defaults templating and
PKCE branches, and ConnectorSettings[T] round-trip plus malformed-JSON
error path. The pre-refactor ApplyProviderDefaults test in
pkg/connector is replaced by the equivalent in
pkg/connector/provider.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/connector/provider/registry.go

@@ -0,0 +1,134 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+// Package provider holds one Go file per connector provider. Each file
+// exposes a private constructor that returns a *Registration; the
+// builtin set is assembled by NewBuiltinRegistry, which probod calls
+// once at startup and threads as an explicit *Registry into every
+// consumer. The registry carries no package-level state.
+//
+// pkg/connector/provider is a sub-package of pkg/connector. The
+// child may import its parent (it does — for the *OAuth2Connector
+// type in apply.go); the parent must not import this child. Cycles
+// with pkg/coredata are avoided because the back-edge runs:
+// provider -> connector -> coredata -> (no further imports back).
+package provider
+
+import (
+	"fmt"
+	"slices"
+	"sync"
+
+	"go.probo.inc/probo/pkg/coredata"
+)
+
+// Registry holds the per-provider *Registration set used by the rest
+// of the system to look up display names, OAuth2 metadata, driver
+// constructors, and so on. It is safe for concurrent use.
+//
+// All consumers receive a *Registry constructed by NewBuiltinRegistry
+// at probod startup; no package-level singleton exists.
+type Registry struct {
+	mu        sync.RWMutex
+	providers map[coredata.ConnectorProvider]*Registration
+}
+
+// NewRegistry returns an empty *Registry. Production code uses
+// NewBuiltinRegistry; tests and specialised callers can construct an
+// empty Registry and register only the providers they need.
+func NewRegistry() *Registry {
+	return &Registry{
+		providers: make(map[coredata.ConnectorProvider]*Registration),
+	}
+}
+
+// Register adds a Registration to r. It returns an error on nil or
+// incomplete Registration metadata or on duplicate registration so
+// callers (in particular NewBuiltinRegistry) can decide whether the
+// condition is a programmer error worth crashing on or a recoverable
+// state worth surfacing.
+func (r *Registry) Register(reg *Registration) error {
+	if reg == nil {
+		return fmt.Errorf("cannot register connector provider: nil Registration")
+	}
+
+	if reg.Provider == "" {
+		return fmt.Errorf("cannot register connector provider: missing Provider")
+	}
+
+	if reg.DisplayName == "" {
+		return fmt.Errorf("cannot register connector provider %q: missing DisplayName", reg.Provider)
+	}
+
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if _, dup := r.providers[reg.Provider]; dup {
+		return fmt.Errorf("cannot register connector provider %q: duplicate registration", reg.Provider)
+	}
+
+	r.providers[reg.Provider] = reg
+
+	return nil
+}
+
+// Get returns the Registration for the given provider, or false if
+// no provider is registered under that key.
+func (r *Registry) Get(p coredata.ConnectorProvider) (*Registration, bool) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	reg, ok := r.providers[p]
+
+	return reg, ok
+}
+
+// All returns every Registration currently in r. Order is not stable;
+// callers must sort when determinism matters.
+func (r *Registry) All() []*Registration {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	out := make([]*Registration, 0, len(r.providers))
+	for _, reg := range r.providers {
+		out = append(out, reg)
+	}
+
+	return out
+}
+
+// ProviderDisplayName returns the human-readable label for the
+// provider, falling back to the raw constant string when no display
+// name is registered.
+func (r *Registry) ProviderDisplayName(p coredata.ConnectorProvider) string {
+	if reg, ok := r.Get(p); ok && reg.DisplayName != "" {
+		return reg.DisplayName
+	}
+
+	return string(p)
+}
+
+// ProviderOAuth2Scopes returns the OAuth2 scopes the access review
+// driver for the given provider needs to list user accounts. Returns
+// nil for providers that do not need any scopes (Notion, Intercom)
+// or for non-access-review providers.
+func (r *Registry) ProviderOAuth2Scopes(p coredata.ConnectorProvider) []string {
+	if reg, ok := r.Get(p); ok {
+		// Return a copy so callers cannot mutate the shared, concurrently
+		// read registration slice held by this long-lived registry.
+		return slices.Clone(reg.OAuth2Scopes)
+	}
+
+	return nil
+}