fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN12-LIBGCRYPT20-1550206
- https://snyk.io/vuln/SNYK-DEBIAN12-OPENSSL-1555825
- https://snyk.io/vuln/SNYK-DEBIAN12-OPENSSL-1555825
- https://snyk.io/vuln/SNYK-DEBIAN12-OPENSSL-1555907
- https://snyk.io/vuln/SNYK-DEBIAN12-ZLIB-6008963

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3-slim AS builder
+FROM python:3.12.0b1-slim AS builder
 ADD . /app
 WORKDIR /app