feat: migrate auth0mock from Node.js to Go

Refactor the application to a Go-based architecture for improved
performance and maintainability. Replace the Dockerfile to utilize a
multi-stage build process, enhancing image efficiency. Implement
comprehensive session store tests to ensure reliability and create
new OAuth handlers for managing authentication efficiently. Update 
documentation to reflect these structural changes.

Dockerfile

@@ -1,12 +1,26 @@
-FROM amd64/node:24.12.0@sha256:e8bb5aafe1964147c8344b1ea7698218e3675340407a07a14c49901df97455f6
+FROM golang:1.24 AS build
+
+ARG GITLAB_USER
+ARG GITLAB_TOKEN
+
+WORKDIR /build
+ENV CGO_ENABLED=0
+ENV GOPRIVATE=gitlab.com/unboundsoftware/*
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN go build -ldflags="-s -w" -o /release/service ./cmd/service
+
+FROM gcr.io/distroless/static-debian12
+
+ENV TZ=Europe/Stockholm
 ENV AUDIENCE="https://shiny.unbound.se"
-ENV ORIGIN_HOST="auth0mock"
-ENV ORIGIN="https://auth0mock:3333"
+
+COPY --from=build /release/service /service
+COPY public /public
+
 EXPOSE 3333
-WORKDIR /app
-ADD package.json yarn.lock /app/
-RUN yarn install --frozen-lockfile
-ADD *.js /app/
-ADD public /app/public
-RUN mkdir -p /root/.config
-ENTRYPOINT ["yarn", "start"]
+
+ENTRYPOINT ["/service"]