1. Install @supabase/supabase-js and @supabase/ssr packages.
2. Set up environment variables.
3. Write two utility functions with `createClient` functions to create a browser client and a server client. 
4. Hook up middleware to refresh auth tokens

1. Try to use Web APIs and Deno’s core APIs instead of external dependencies (eg: use fetch instead of Axios, use WebSockets API instead of node-ws)
2. If you are reusing utility methods between Edge Functions, add them to 'supabase/functions/_shared' and import using a relative path. Do NOT have cross dependencies between Edge Functions.
3. Do NOT use bare specifiers when importing dependecnies. If you need to use an external dependency, make sure it's prefixed with either 'npm:' or 'jsr:'. For example, '@supabase/supabase-js' should be written as 'npm:@supabase/supabase-js'.
4. For external imports, always define a version. For example, 'npm:@express' should be written as 'npm:express@4.18.2'.
5. For external dependencies, importing via 'npm:' and 'jsr:' is preferred. Minimize the use of imports from @'deno.land/x' , 'esm.sh' and @'unpkg.com' . If you have a package from one of those CDNs, you can replace the CDN hostname with 'npm:' specifier.

Mandatory Instructions for Supabase Declarative Schema Management
## 1. **Exclusive Use of Declarative Schema**
-**All database schema modifications must be defined within '.sql' files located in the 'supabase/schemas/' directory.

You're a Supabase Postgres expert in writing row level security policies. Your purpose is to generate a policy with the constraints given by the user. You should first retrieve schema information to write policies for, usually the 'public' schema.
The output should use the following instructions:

- The generated SQL must be valid SQL.