chore: fix login integration (#10318)

# Which Problems Are Solved

Login integration tests are not executed in the pipeline

# How the Problems Are Solved

The login integration tests are fixed and added as a pipeline workflow.
It  tests against the built login docker image.
On pipeline failures, developers are guided on how to fix them using a
dev container configured for this purpose.

# Additional Changes

- email domains are replaced by example.com. In case the tests were
accidentally run against a cloud instance, it wouldn't cause bounces.
- pnpm is upgraded, because the --filter argument doesn't work for the
install command on the old version.
- The login Dockerfile is optimized for docker image builds

# Additional Changes From Review for
https://github.com/zitadel/zitadel/pull/10305

These changes were requested from @peintnermax 

- The base dev container starts without any services besides the
database and the dev container itself
- CONTRIBUTING.md is restructured
- To reproduce pipeline checks, only the devcontainer CLI and Docker are
needed. This is described in the CONTRIBUTING.md
- The convenience npm script "generate" is added

# Additional Context

- Follow-up for PR https://github.com/zitadel/zitadel/pull/10305
- Base for https://github.com/zitadel/zitadel/issues/10277

build/login/Dockerfile

@@ -1,34 +1,43 @@
-FROM node:20-alpine AS base
+FROM node:20-alpine AS runtime
 
-FROM base AS build
+FROM runtime AS pnpm-base
+RUN apk add --no-cache libc6-compat
 ENV PNPM_HOME="/pnpm"
 ENV PATH="$PNPM_HOME:$PATH"
-RUN corepack enable && COREPACK_ENABLE_DOWNLOAD_PROMPT=0 corepack prepare pnpm@9.1.2 --activate && \
-    apk update && apk add --no-cache && \
-    rm -rf /var/cache/apk/*
-WORKDIR /app
-COPY pnpm-lock.yaml pnpm-workspace.yaml  ./
-RUN --mount=type=cache,id=pnpm,target=/root/.local/share/pnpm/store pnpm fetch --frozen-lockfile \
-    --filter @zitadel/login \
-    --filter @zitadel/client \
-    --filter @zitadel/proto
-COPY package.json ./
-COPY apps/login/package.json ./apps/login/package.json
-COPY packages/zitadel-proto/package.json ./packages/zitadel-proto/package.json
-COPY packages/zitadel-client/package.json ./packages/zitadel-client/package.json
-RUN --mount=type=cache,id=pnpm,target=/root/.local/share/pnpm/store pnpm install --frozen-lockfile \
-    --filter @zitadel/login \
-    --filter @zitadel/client \
-    --filter @zitadel/proto
+RUN corepack enable && corepack prepare pnpm@10.13.1 --activate
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
+    pnpm add -g turbo@2.5.5
+
+FROM pnpm-base AS pruner
+WORKDIR /prune
 COPY . .
-RUN pnpm turbo build:login:standalone
+RUN pnpm turbo prune @zitadel/login @zitadel/client @zitadel/proto --docker
+
+FROM pnpm-base AS installer
+WORKDIR /install
+COPY --from=pruner /prune/out/pnpm-lock.yaml ./
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
+    pnpm fetch --frozen-lockfile
+COPY --from=pruner /prune/out/json/ .
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
+    pnpm install --frozen-lockfile --ignore-scripts
+
+FROM pnpm-base AS builder
+WORKDIR /build
+COPY --from=installer /install/ .
+COPY --from=pruner /prune/out/full/ .
+COPY proto ./proto
+ENV CI=true
+RUN --mount=type=cache,id=turbo,target=/build/.turbo/cache \
+    --mount=type=cache,id=next,target=/build/apps/login/.next/cache \
+    pnpm turbo build:login:standalone --cache-dir=/build/.turbo/cache
 
 FROM scratch AS build-out
 COPY /apps/login/public ./apps/login/public
-COPY --from=build /app/apps/login/.next/standalone ./
-COPY --from=build /app/apps/login/.next/static ./apps/login/.next/static
+COPY --from=builder /build/apps/login/.next/standalone ./
+COPY --from=builder /build/apps/login/.next/static ./apps/login/.next/static
 
-FROM base AS login-standalone
+FROM runtime AS login-standalone
 WORKDIR /runtime
 RUN addgroup --system --gid 1001 nodejs && \
     adduser --system --uid 1001 nextjs
@@ -36,10 +45,11 @@ RUN addgroup --system --gid 1001 nodejs && \
 RUN mkdir -p /.env-file && touch /.env-file/.env && chown -R nextjs:nodejs /.env-file
 COPY --chown=nextjs:nodejs apps/login/scripts ./
 COPY --chown=nextjs:nodejs --from=build-out . .
+# Debug the final structure
 USER nextjs
 ENV HOSTNAME="0.0.0.0"
 ENV PORT=3000
 # TODO: Check healthy, not ready
 HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
-    CMD ["/bin/sh", "-c", "node ./healthcheck.js http://localhost:${PORT}/ui/v2/login/healthy"]
-ENTRYPOINT ["./entrypoint.sh"]
+    CMD ["/bin/sh", "-c", "node /runtime/healthcheck.js http://localhost:${PORT}/ui/v2/login/healthy"]
+ENTRYPOINT ["/runtime/entrypoint.sh"]