feat: Initial Login flow (#42)

This just implements a basic sign-in flow, using the new endpoints in #29 :
![2022-01-20 12 35 30](https://user-images.githubusercontent.com/88213859/150418044-85900d1f-8890-4c60-baae-234342de71fa.gif)

This brings over several dependencies that are necessary:
- `formik`
- `yep`

Ports over some v1 code to bootstrap it:
- `FormTextField`
- `PasswordField`
- `CoderIcon`

And implements basic sign-in:
Fixes #37 
Fixes #43

This does not implement it navbar integration (importantly - there is no way to sign out yet, unless you manually delete your `session_token`). I'll do that in the next PR - figured this was big enough to get reviewed.

site/components/Button/LoadingButton.test.tsx

@@ -0,0 +1,23 @@
+import { render, screen } from "@testing-library/react"
+import React from "react"
+import { LoadingButton } from "./LoadingButton"
+
+describe("LoadingButton", () => {
+  it("renders", async () => {
+    // When
+    render(<LoadingButton>Sign In</LoadingButton>)
+
+    // Then
+    const element = await screen.findByText("Sign In")
+    expect(element).toBeDefined()
+  })
+
+  it("shows spinner if loading is set to true", async () => {
+    // When
+    render(<LoadingButton loading>Sign in</LoadingButton>)
+
+    // Then
+    const spinnerElement = await screen.findByRole("progressbar")
+    expect(spinnerElement).toBeDefined()
+  })
+})

site/components/Button/LoadingButton.tsx

@@ -0,0 +1,45 @@
+import Button, { ButtonProps } from "@material-ui/core/Button"
+import CircularProgress from "@material-ui/core/CircularProgress"
+import { makeStyles } from "@material-ui/core/styles"
+import * as React from "react"
+
+export interface LoadingButtonProps extends ButtonProps {
+  /** Whether or not to disable the button and show a spinner */
+  loading?: boolean
+}
+
+/**
+ * LoadingButton is a small wrapper around Material-UI's button to show a loading spinner
+ *
+ * In Material-UI 5+ - this is built-in, but since we're on an earlier version,
+ * we have to roll our own.
+ */
+export const LoadingButton: React.FC<LoadingButtonProps> = ({ loading = false, children, ...rest }) => {
+  const styles = useStyles()
+  const hidden = loading ? { opacity: 0 } : undefined
+
+  return (
+    <Button {...rest} disabled={rest.disabled || loading}>
+      <span style={hidden}>{children}</span>
+      {loading && (
+        <div className={styles.loader}>
+          <CircularProgress size={18} className={styles.spinner} />
+        </div>
+      )}
+    </Button>
+  )
+}
+
+const useStyles = makeStyles((theme) => ({
+  loader: {
+    position: "absolute",
+    top: "50%",
+    left: "50%",
+    transform: "translate(-50%, -50%)",
+    height: 18,
+    width: 18,
+  },
+  spinner: {
+    color: theme.palette.text.disabled,
+  },
+}))

site/components/Button/index.ts

@@ -1 +1,2 @@
-export { SplitButton } from "./SplitButton"
+export * from "./SplitButton"
+export * from "./LoadingButton"