How to create a Postgres database that has an upper-case letter in the name

Answer: Surround the name with quotes!

Like so:

CREATE DATABASE "MyAwesomeDatabase";

It looks like this in psql session:

psql (14.5, server 12.9)
Type "help" for help.

postgres=# CREATE DATABASE "MyAwesomeDatabase";
CREATE DATABASE
postgres=# \l
                                        List of databases
           Name           |  Owner   | Encoding |  Collate   |   Ctype    |   Access privileges
--------------------------+----------+----------+------------+------------+-----------------------
 MyAwesomeDatabase        | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
 postgres                 | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
(2 rows)

If you don't include quotes, you'll create a database with all lowercase letters:

psql (14.5, server 12.9)
Type "help" for help.

postgres=# CREATE DATABASE MyAwesomeDatabase;
CREATE DATABASE
postgres=# \l
                                        List of databases
           Name           |  Owner   | Encoding |  Collate   |   Ctype    |   Access privileges
--------------------------+----------+----------+------------+------------+-----------------------
 myawesomedatabase        | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
 postgres                 | postgres | UTF8     | en_US.utf8 | en_US.utf8 |
(2 rows)