Provide a SQL script as release artifact

[steve-chavez]

Problem

While we're a pg extension, doing make && sudo make install is still more cumbersome than running a SQL script (psql -f script.sql).

Solution

Include a single SQL file as a release artifact. Newer versions can have a single script plus an upgrade script too (like postgrest-openapi--0.1.0--0.1.1.sql).

[steve-chavez]

plus an upgrade script too (like postgrest-openapi--0.1.0--0.1.1.sql).

Since we're only functions, maybe we can omit this and just drop and recreate.