add user deletion

doc/database_spec.md

···
 | `id`      | int  | identifier for this entry             |
 | `post_id` | int  | the post this entry is for            |
 | `likes`   | int  | the net amount of likes this post has |
+
+## `Site`
+
+> stores mutable, site-wide data. there should only ever be one entry here
+
+| name   | type   | desc                                         |
+|--------|--------|----------------------------------------------|
+| `id`   | int    | identifier for this (should always be 0)     |
+| `motd` | string | the message of the day displayed on `/index` |
+
+## `Notification`
+
+> represents a notification sent to a user
+
+| name      | type   | desc                                     |
+|-----------|--------|------------------------------------------|
+| `id`      | int    | identifier for this notification         |
+| `user_id` | int    | the user that receives this notification |
+| `summary` | string | the summary for this notification        |
+| `body`    | string | the full text for this notification      |

doc/todo.md

···
 - [ ] post:tags ('hashtags')
 - [ ] post:images (should have a config.maple toggle to enable/disable)
 - [ ] post:saving (add the post to a list of saved posts that a user can view later)
-- [ ] user:deletion
 
 ## ideas
 
···
 - [x] user:bio/about me
 - [x] user:listed pronouns
 - [x] user:notifications
+- [x] user:deletion
 - [x] post:likes/dislikes
 - [x] post:mentioning ('tagging') other users in posts
 	- [x] post:mentioning:who mentioned you (send notifications when a user mentions you)

readme.md

···
 ```
 
 then go to the configured url to view (default is `http://localhost:8008`).
+
+if you do not have a database, you can either self-host a postgresql database on
+your machine, or you can find a free one online. i use and like
+[neon.tech](https://neon.tech), their free plan is pretty comfortable for a
+small beep instance!

src/api.v

···
 	return ctx.redirect('/inbox')
 }
 
+@['/api/user/delete']
+fn (mut app App) api_user_delete(mut ctx Context, id int) veb.Result {
+	user := app.whoami(mut ctx) or {
+		ctx.error('you are not logged in!')
+		return ctx.redirect('/login')
+	}
+
+	println('attempting to delete ${id} as ${user.id}')
+
+	if user.admin || user.id == id {
+		// yeet
+		sql app.db {
+			delete from User where id == id
+			delete from Like where user_id == id
+			delete from Notification where user_id == id
+		} or {
+			ctx.error('failed to delete user: ${id}')
+			return ctx.redirect('/')
+		}
+
+		// delete posts and their likes
+		posts_from_this_user := sql app.db {
+			select from Post where author_id == id
+		} or { [] }
+
+		for post in posts_from_this_user {
+			sql app.db {
+				delete from Like where post_id == post.id
+				delete from LikeCache where post_id == post.id
+			} or {
+				eprintln('failed to delete like cache for post during user deletion: ${post.id}')
+			}
+		}
+
+		sql app.db {
+			delete from Post where author_id == id
+		} or {
+			eprintln('failed to delete posts by deleting user: ${user.id}')
+		}
+
+		app.auth.delete_tokens_for_user(id) or {
+			eprintln('failed to delete tokens for user during deletion: ${id}')
+		}
+		// log out
+		if user.id == id {
+			ctx.set_cookie(
+				name:      'token'
+				value:     ''
+				same_site: .same_site_none_mode
+				secure:    true
+				path:      '/'
+			)
+		}
+		println('deleted user ${id}')
+	} else {
+		ctx.error('be nice. deleting other users is off-limits.')
+	}
+
+	return ctx.redirect('/')
+}
+
 ////// post //////
 
 @['/api/post/new_post'; post]

src/templates/user.html

···
 		<input type="submit" value="save">
 	</form>
 	@end
+	<br>
+	<details>
+		<summary>dangerous settings (click to reveal)</summary>
+		<div>
+			<form action="/api/user/delete" autocomplete="off">
+				<input
+					type="number"
+					name="id"
+					id="id"
+					value="@user.id"
+					required
+					readonly
+					hidden
+					aria-hidden
+				>
+				<p><strong>there is NO GOING BACK after deleting your account.</strong></p>
+				<p><strong>EVERY ONE of your posts, notifications, likes, dislikes, and ALL OTHER USER DATA WILL BE PERMANENTLY DELETED</strong></p>
+				<div>
+					<input type="checkbox" name="are-you-sure" id="are-you-sure" required>
+					<label for="are-you-sure">click to confirm</label>
+				</div>
+				<br>
+				<div>
+					<input type="checkbox" name="are-you-really-sure" id="are-you-really-sure" required>
+					<label for="are-you-really-sure">click to doubly confirm</label>
+				</div>
+				<br>
+				<div>
+					<input type="checkbox" name="are-you-absolutely-sure" id="are-you-absolutely-sure" required>
+					<label for="are-you-absolutely-sure">click to triply confirm</label>
+				</div>
+				<br>
+				<input type="submit" value="delete your account">
+			</form>
+		</div>
+	</details>
 </div>
 @end
 
···
 	<h2>admin powers:</h2>
 	<form action="/api/user/set_muted" method="post">
 		<input
-			type="text"
+			type="number"
 			name="id"
 			id="id"
 			value="@user.id"