chore: integrate wkhtmltopdf into docker build process

Dockerfile

@@ -6,14 +6,18 @@ FROM golang:1.19 as builder
 # Create and change to the app directory.
 WORKDIR /app
 
+# Install wkhtmltopdf in the builder stage.
+RUN apt-get update && apt-get install -y wkhtmltopdf && apt-get clean
+
 # Copy go.sum/go.mod and warm up the module cache (so that this
 # rather long step can be cached if go.mod/go.sum don't change)
 COPY go.* ./
 RUN go mod download
 
+# Set the environment variable for Gin in release mode.
 ENV GIN_MODE release
 
-# Now copy the rest.
+# Now copy the rest
 COPY . .
 
 # Build the binary.
@@ -22,10 +26,16 @@ RUN CGO_ENABLED=0 GOOS=linux go build -v -o server github.com/savannahghi/clinic
 # Use the official Alpine image for a lean production container.
 # https://hub.docker.com/_/alpine
 # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
-FROM alpine:3
-RUN apk add --no-cache ca-certificates wkhtmltopdf
+FROM alpine:3 as production
+
+# Install ca-certificates for SSL.
+RUN apk add --no-cache ca-certificates
+
+# Copy the wkhtmltopdf binary from the builder stage to the production image.
+# The path /usr/bin/wkhtmltopdf is typical for Debian-based installations; adjust if necessary.
+COPY --from=builder /usr/bin/wkhtmltopdf /usr/local/bin/
 
-# Copy the binary to the production image from the builder stage.
+# Copy the Go binary to the production image from the builder stage.
 COPY --from=builder /app/server /server
 
 # Run the web service on container startup.