User accounts

Allows for the creation of user accounts. A few notes on the specifics:

 - Experiments are the main access control objects. If you can view an experiment, you can view all its prompts/scenarios/evals. If you can edit it, you can edit or delete all of those as well.
 - Experiments are owned by Organizations in the database. Organizations can have multiple members and members can have roles of ADMIN, MEMBER or VIEWER.
 - Organizations can either be "personal" or general. Each user has a "personal" organization created as soon as they try to create an experiment. There's currently no UI support for creating general orgs or adding users to them; they're just in the database to future-proof all the ACL logic.
 - You can require that a user is signed-in to see a route using the `protectedProcedure` helper. When you use `protectedProcedure`, you also have to call `ctx.markAccessControlRun()` (or delegate to a function that does it for you; see accessControl.ts). This is to remind us to actually check for access control when we define a new endpoint.

src/components/nav/UserMenu.tsx

@@ -0,0 +1,72 @@
+import {
+  HStack,
+  Icon,
+  Image,
+  VStack,
+  Text,
+  Popover,
+  PopoverTrigger,
+  PopoverContent,
+  Link,
+} from "@chakra-ui/react";
+import { type Session } from "next-auth";
+import { signOut } from "next-auth/react";
+import { BsBoxArrowRight, BsChevronRight, BsPersonCircle } from "react-icons/bs";
+
+export default function UserMenu({ user }: { user: Session }) {
+  const profileImage = user.user.image ? (
+    <Image src={user.user.image} alt="profile picture" w={8} h={8} borderRadius="50%" />
+  ) : (
+    <Icon as={BsPersonCircle} boxSize="md" />
+  );
+
+  return (
+    <>
+      <Popover placement="right">
+        <PopoverTrigger>
+          <HStack
+            px={2}
+            py={2}
+            borderColor={"gray.200"}
+            borderTopWidth={1}
+            borderBottomWidth={1}
+            cursor="pointer"
+            _hover={{
+              bgColor: "gray.200",
+            }}
+          >
+            {profileImage}
+            <VStack spacing={0} align="start" flex={1}>
+              <Text fontWeight="bold" fontSize="sm">
+                {user.user.name}
+              </Text>
+              <Text color="gray.500" fontSize="xs">
+                {user.user.email}
+              </Text>
+            </VStack>
+            <Icon as={BsChevronRight} boxSize={4} color="gray.500" />
+          </HStack>
+        </PopoverTrigger>
+        <PopoverContent _focusVisible={{ boxShadow: "unset", outline: "unset" }} maxW="200px">
+          <VStack align="stretch" spacing={0}>
+            {/* sign out */}
+            <HStack
+              as={Link}
+              onClick={() => {
+                signOut().catch(console.error);
+              }}
+              px={4}
+              py={2}
+              spacing={4}
+              color="gray.500"
+              fontSize="sm"
+            >
+              <Icon as={BsBoxArrowRight} boxSize={6} />
+              <Text>Sign out</Text>
+            </HStack>
+          </VStack>
+        </PopoverContent>
+      </Popover>
+    </>
+  );
+}