add a way to try sqlpage.hash_password online

Author: lovasoa

examples/official-site/examples/hash_password.sql

@@ -0,0 +1,42 @@
+select 'text' as component, '
+
+# Password Hashing
+
+In SQLPage, you can use the [`sqlpage.hash_password`](/functions.sql?function=hash_password) function to
+create a sequence of letters and numbers that can be used to verify
+a password, but cannot be used to recover the password itself.
+This is called a [hash](https://en.wikipedia.org/wiki/Hash_function) of the password,
+and it is a common way to store passwords in a database.
+This way, even if someone gains access to the database, they cannot
+recover the passwords.
+
+They could still try to guess the passwords, but since SQLPage
+uses the [argon2](https://en.wikipedia.org/wiki/Argon2) algorithm,
+it would take a very long time (multiple years) to guess a strong password.
+
+The `sqlpage.hash_password` function takes a password as input, and
+returns a hash of the password as output. It takes some time
+(a few hundred milliseconds) to compute the hash, so you should
+only call it when the user is creating a new account and on the initial
+login. You should not call it on every page load.
+
+# Try it out
+
+You can try the password hashing function out by entering a password
+below and clicking "Hash Password".
+' as contents_md;
+
+select 'form' as component, 'Hash Password' as validate;
+select 'password' as type, 'password' as name, 'Password' as label, 'Enter a password to hash' as placeholder;
+
+select 'text' as component, '
+
+### Hashed Password
+
+The password you entered above hashed to the following value:
+
+```sql
+' || sqlpage.hash_password(:password) || '
+```
+' as contents_md
+where :password is not null;

examples/official-site/sqlpage/migrations/07_authentication.sql

@@ -57,17 +57,20 @@ VALUES (
 The most basic usage of the authentication component is to let SQLPage handle the authentication through HTTP basic authentication.
 This is the simplest way to password-protect a page, but it is not very user-friendly, because the browser will show an unstyled popup asking for the username and password.
 The username and password entered by the user will be accessible in your SQL code using the
-[`sqlpage.basic_auth_username()`](functions.sql?function=basic_auth_username) and
-[`sqlpage.basic_auth_password()`](functions.sql?function=basic_auth_password) functions.
+[`sqlpage.basic_auth_username()`](functions.sql?function=basic_auth_username#function) and
+[`sqlpage.basic_auth_password()`](functions.sql?function=basic_auth_password#function) functions.
 
-The [`sqlpage.hash_password`](functions.sql?function=hash_password) function can be used to generate a secure password hash that you need to store in your database.
+The [`sqlpage.hash_password`](functions.sql?function=hash_password#function) function can be used to 
+[generate a secure password hash](/examples/hash_password.sql) that you need to store in your database.
 
 ```sql
 SELECT ''authentication'' AS component,
     ''$argon2id$v=19$m=16,t=2,p=1$TERTd0lIcUpraWFTcmRQYw$+bjtag7Xjb6p1dsuYOkngw'' AS password_hash, -- generated using sqlpage.hash_password
     sqlpage.basic_auth_password() AS password; -- this is the password that the user entered in the browser popup
 ```
 
+You can [try the hash_password function out here](/examples/hash_password.sql).
+
 ### Usage with a login form
 
 The most basic usage of the authentication component is to simply check if the user has sent the correct password, and if not, redirect them to a login page: 

examples/official-site/sqlpage/migrations/08_functions.sql

@@ -139,8 +139,9 @@ VALUES (
         'hash_password',
         '0.7.2',
         'spy',
-        'Hashes a password using the [Argon2](https://en.wikipedia.org/wiki/Argon2) algorithm.
-    The resulting hash can be stored in the database and then used with the [authentication component](documentation.sql?component=authentication#component).
+        '
+Hashes a password using the [Argon2](https://en.wikipedia.org/wiki/Argon2) algorithm.
+The resulting hash can be stored in the database and then used with the [authentication component](documentation.sql?component=authentication#component).
 
 ### Example
 
@@ -151,6 +152,10 @@ SELECT ''password'' AS name, ''password'' AS type;
 
 INSERT INTO users (name, password_hash) VALUES (:username, sqlpage.hash_password(:password));
 ```
+
+### Try online
+
+You can try the password hashing function [on this page](/examples/hash_password.sql).
     '
     );
 INSERT INTO sqlpage_function_parameters (