Add user sessions and login

This isn't quite perfect, but gets much of the hard work done.

templates/dashboard.html

@@ -0,0 +1,9 @@
+{{template "base.html" .}}
+
+{{define "title"}}Dash{{end}}
+{{define "style"}}
+{{end}}
+{{define "content"}}
+<h1>Hey {{ .Username }}</h1>
+<p>At this point, pretend I'm showing you the result of some ArcGIS data.</p>
+{{end}}

templates/signin.html

@@ -33,22 +33,23 @@
 					<p class="text-muted">Please enter your credentials</p>
 				</div>
 					
-				<form>
+				<form method="POST" action="/signin">
 					<div class="mb-3">
 						<label for="username" class="form-label">Username</label>
-						<input type="text" class="form-control" id="username" required>
+						<input type="text" class="form-control" name="username" required>
 					</div>
 					
 					<div class="mb-3">
 						<label for="password" class="form-label">Password</label>
-						<input type="password" class="form-control" id="password" required>
+						<input type="password" class="form-control" name="password" required>
 					</div>
 					
-					<div class="mb-3 form-check">
-						<input type="checkbox" class="form-check-input" id="remember">
-						<label class="form-check-label" for="remember">Remember me</label>
+					{{ if .InvalidCredentials }}
+					<div class="alert alert-danger" role="alert">
+						The credentials you provided weren't recognized.
 					</div>
-					
+					{{ end }}
+
 					<div class="d-grid gap-2">
 						<button type="submit" class="btn btn-primary">Login</button>
 					</div>