storagemanager: Add keyval+ (combined keyval + map) store type

This combines the two most common store types, which modules often end up
opening with both interfaces separately anyway.

As well as combining them, I've taken the opportunity to improve some of the
method names to make them clearer.

spec/core_storagemanager_spec.lua

@@ -196,6 +196,136 @@ describe("storagemanager", function ()
 				end);
 			end);
 
+			describe("keyval+ stores", function ()
+				-- These tests rely on being executed in order, disable any order
+				-- randomization for this block
+				randomize(false);
+
+				local store, kv_store, map_store;
+				it("may be opened", function ()
+					store = assert(sm.open(test_host, "test-kv+", "keyval+"));
+				end);
+
+				local simple_data = { foo = "bar" };
+
+				it("may set data for a user", function ()
+					assert(store:set("user9999", simple_data));
+				end);
+
+				it("may get data for a user", function ()
+					assert.same(simple_data, assert(store:get("user9999")));
+				end);
+
+				it("may be opened as a keyval store", function ()
+					kv_store = assert(sm.open(test_host, "test-kv+", "keyval"));
+					assert.same(simple_data, assert(kv_store:get("user9999")));
+				end);
+
+				it("may be opened as a map store", function ()
+					map_store = assert(sm.open(test_host, "test-kv+", "map"));
+					assert.same("bar", assert(map_store:get("user9999", "foo")));
+				end);
+
+				it("may remove data for a user", function ()
+					assert(store:set("user9999", nil));
+					local ret, err = store:get("user9999");
+					assert.is_nil(ret);
+					assert.is_nil(err);
+				end);
+
+
+				it("may set a specific key for a user", function ()
+					assert(store:set_key("user9999", "foo", "bar"));
+					assert.same(kv_store:get("user9999"), { foo = "bar" });
+				end);
+
+				it("may get a specific key for a user", function ()
+					assert.equal("bar", store:get_key("user9999", "foo"));
+				end);
+
+				it("may find all users with a specific key", function ()
+					assert.is_function(store.get_key_from_all);
+					assert(store:set_key("user9999b", "bar", "bar"));
+					assert(store:set_key("user9999c", "foo", "blah"));
+					local ret, err = store:get_key_from_all("foo");
+					assert.is_nil(err);
+					assert.same({ user9999 = "bar", user9999c = "blah" }, ret);
+				end);
+
+				it("rejects empty or non-string keys to get_all", function ()
+					assert.is_function(store.get_key_from_all);
+					do
+						local ret, err = store:get_key_from_all("");
+						assert.is_nil(ret);
+						assert.is_not_nil(err);
+					end
+					do
+						local ret, err = store:get_key_from_all(true);
+						assert.is_nil(ret);
+						assert.is_not_nil(err);
+					end
+				end);
+
+				it("rejects empty or non-string keys to delete_all", function ()
+					assert.is_function(store.delete_key_from_all);
+					do
+						local ret, err = store:delete_key_from_all("");
+						assert.is_nil(ret);
+						assert.is_not_nil(err);
+					end
+					do
+						local ret, err = store:delete_key_from_all(true);
+						assert.is_nil(ret);
+						assert.is_not_nil(err);
+					end
+				end);
+
+				it("may delete all instances of a specific key", function ()
+					assert.is_function(store.delete_key_from_all);
+					assert(store:set_key("user9999b", "foo", "hello"));
+
+					assert(store:delete_key_from_all("bar"));
+					-- Ensure key was deleted
+					do
+						local ret, err = store:get_key("user9999b", "bar");
+						assert.is_nil(ret);
+						assert.is_nil(err);
+					end
+					-- Ensure other users/keys are intact
+					do
+						local ret, err = store:get_key("user9999", "foo");
+						assert.equal("bar", ret);
+						assert.is_nil(err);
+					end
+					do
+						local ret, err = store:get_key("user9999b", "foo");
+						assert.equal("hello", ret);
+						assert.is_nil(err);
+					end
+					do
+						local ret, err = store:get_key("user9999c", "foo");
+						assert.equal("blah", ret);
+						assert.is_nil(err);
+					end
+				end);
+
+				it("may remove data for a specific key for a user", function ()
+					assert(store:set_key("user9999", "foo", nil));
+					do
+						local ret, err = store:get_key("user9999", "foo");
+						assert.is_nil(ret);
+						assert.is_nil(err);
+					end
+
+					assert(store:set_key("user9999b", "foo", nil));
+					do
+						local ret, err = store:get_key("user9999b", "foo");
+						assert.is_nil(ret);
+						assert.is_nil(err);
+					end
+				end);
+			end);
+
 			describe("archive stores", function ()
 				randomize(false);