feat(oauth-gateway): implement multi-tenant OAuth gateway service

- Added a new OAuth gateway service to handle multi-tenant authentication callbacks.
- Implemented routing logic for provider callbacks, including tenant slug validation and host resolution.
- Introduced configuration management for environment variables and service settings.
- Created Dockerfile and package.json for service deployment and dependencies.
- Added HTML response for restricted tenant access and updated static web components accordingly.

Signed-off-by: Innei <tukon479@gmail.com>

be/apps/oauth-gateway/Dockerfile

@@ -0,0 +1,29 @@
+# syntax=docker/dockerfile:1.7
+
+FROM node:20-alpine AS base
+ENV PNPM_HOME=/pnpm
+ENV PATH="$PNPM_HOME:$PATH"
+RUN corepack enable && corepack prepare pnpm@10.19.0 --activate
+
+FROM base AS builder
+WORKDIR /workspace
+
+COPY package.json pnpm-workspace.yaml pnpm-lock.yaml ./
+COPY be/apps/oauth-gateway/package.json be/apps/oauth-gateway/package.json
+
+RUN pnpm fetch --filter '@afilmory/oauth-gateway...'
+
+COPY . .
+
+RUN pnpm install --filter '@afilmory/oauth-gateway...' --frozen-lockfile
+RUN pnpm --filter @afilmory/oauth-gateway build
+
+FROM base AS runner
+ENV NODE_ENV=production
+WORKDIR /app
+
+COPY --from=builder /workspace/be/apps/oauth-gateway/dist ./dist
+
+EXPOSE 8790
+
+CMD ["node", "./dist/main.js"]