Add a type for in-memory caching of upstream OIDC Identity Providers

Signed-off-by: Ryan Richard <richardry@vmware.com>

internal/oidc/provider/dynamic_upstream_idp_provider.go

@@ -0,0 +1,52 @@
+// Copyright 2020 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package provider
+
+import (
+	"net/url"
+	"sync"
+)
+
+type UpstreamOIDCIdentityProvider struct {
+	// A name for this upstream provider, which will be used as a component of the path for the callback endpoint
+	// hosted by the Supervisor.
+	Name string
+
+	// The Oauth client ID registered with the upstream provider to be used in the authorization flow.
+	ClientID string
+
+	// The Authorization Endpoint fetched from discovery.
+	AuthorizationURL url.URL
+
+	// Scopes to request in authorization flow.
+	Scopes []string
+}
+
+type DynamicUpstreamIDPProvider interface {
+	SetIDPList(oidcIDPs []UpstreamOIDCIdentityProvider)
+	GetIDPList() []UpstreamOIDCIdentityProvider
+}
+
+type dynamicUpstreamIDPProvider struct {
+	oidcProviders []UpstreamOIDCIdentityProvider
+	mutex         sync.RWMutex
+}
+
+func NewDynamicUpstreamIDPProvider() DynamicUpstreamIDPProvider {
+	return &dynamicUpstreamIDPProvider{
+		oidcProviders: []UpstreamOIDCIdentityProvider{},
+	}
+}
+
+func (p *dynamicUpstreamIDPProvider) SetIDPList(oidcIDPs []UpstreamOIDCIdentityProvider) {
+	p.mutex.Lock() // acquire a write lock
+	defer p.mutex.Unlock()
+	p.oidcProviders = oidcIDPs
+}
+
+func (p *dynamicUpstreamIDPProvider) GetIDPList() []UpstreamOIDCIdentityProvider {
+	p.mutex.RLock() // acquire a read lock
+	defer p.mutex.RUnlock()
+	return p.oidcProviders
+}