Use the default SolidCache::Record role

Don't let the ActiveRecord::Base role bleed into the SolidCache
connections. Also ensure that writes are not prevented.

We'll always set up the shard if configured as we may be pointing to the
default shard but with the wrong role and prevent writes setting.

app/models/solid_cache/record.rb

@@ -14,8 +14,8 @@ def disable_instrumentation
       end
 
       def with_shard(shard, &block)
-        if shard && shard != Record.current_shard
-          Record.connected_to(shard: shard, &block)
+        if shard && SolidCache.connects_to
+          connected_to(shard: shard, role: default_role, prevent_writes: false, &block)
         else
           block.call
         end

lib/solid_cache.rb

@@ -22,7 +22,7 @@ def self.each_shard
 
     if (shards = all_shards_config&.keys)
       shards.each do |shard|
-        Record.connected_to(shard: shard) { yield }
+        Record.with_shard(shard) { yield }
       end
     else
       yield

test/unit/solid_cache_test.rb

@@ -33,6 +33,15 @@ class SolidCacheTest < ActiveSupport::TestCase
     end
   end
 
+  test "each_shard uses the default role" do
+    role = ActiveRecord::Base.connected_to(role: :reading) { SolidCache.each_shard.map { SolidCache::Record.current_role } }
+    if ENV["NO_CONNECTS_TO"]
+      assert_equal [ :reading ], role
+    else
+      assert_equal [ :writing, :writing, :writing, :writing, :writing ], role
+    end
+  end
+
   test "max key bytesize" do
     cache = lookup_store(max_key_bytesize: 100)
     assert_equal 100, cache.send(:normalize_key, SecureRandom.hex(200), {}).bytesize