Fix safari sso header size (#1065)

* Safari SSO header size fix - in progress

* Cleanup of memoryCacheTicketStore

* Redis cache ticket store + registration

* Revert some unecessary changes

* temp - distributed cookie: idsrv.external

* Ticket data cached storage added

* OIDC working w/ substantially reduced cookie size

* Added distributed cache cookie manager

* Removed hybrid OIDC flow

* Enable self-hosted folks to use Redis  for SSO

* Also allow self-hosted to use Redis cont...

src/Core/IdentityServer/MemoryCacheTicketStore.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.Cookies;
+using Microsoft.Extensions.Caching.Memory;
+
+namespace Bit.Core.IdentityServer
+{
+    public class MemoryCacheTicketStore : ITicketStore
+    {
+        private const string _keyPrefix = "auth-";
+        private readonly IMemoryCache _cache;
+
+        public MemoryCacheTicketStore()
+        {
+            _cache = new MemoryCache(new MemoryCacheOptions());
+        }
+
+        public async Task<string> StoreAsync(AuthenticationTicket ticket)
+        {
+            var key = $"{_keyPrefix}{Guid.NewGuid()}";
+            await RenewAsync(key, ticket);
+            return key;
+        }
+
+        public Task RenewAsync(string key, AuthenticationTicket ticket)
+        {
+            var options = new MemoryCacheEntryOptions();
+            var expiresUtc = ticket.Properties.ExpiresUtc;
+            if (expiresUtc.HasValue)
+            {
+                options.SetAbsoluteExpiration(expiresUtc.Value);
+            }
+            else
+            {
+                options.SetSlidingExpiration(TimeSpan.FromMinutes(15));
+            }
+
+            _cache.Set(key, ticket, options);
+
+            return Task.FromResult(0);
+        }
+
+        public Task<AuthenticationTicket> RetrieveAsync(string key)
+        {
+            _cache.TryGetValue(key, out AuthenticationTicket ticket);
+            return Task.FromResult(ticket);
+        }
+
+        public Task RemoveAsync(string key)
+        {
+            _cache.Remove(key);
+            return Task.FromResult(0);
+        }
+    }
+}