Dynamically create the service_conf.yaml file by replacing environment variables from .env (#3341)

### What problem does this PR solve?

This pull request implements the feature mentioned in #3322. 

Instead of manually having to edit the `service_conf.yaml` file when
changes have been made to `.env` and mapping it into the docker
container at runtime, a template file is used and the values replaced by
the environment variables from the `.env` file when the container is
started.
 

### Type of change

- [X] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>
Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>

docker/entrypoint.sh

@@ -1,5 +1,12 @@
 #!/bin/bash
 
+# replace env variables in the service_conf.yaml file
+rm -rf /ragflow/conf/service_conf.yaml
+while IFS= read -r line || [[ -n "$line" ]]; do
+    # Use eval to interpret the variable with default values
+    eval "echo \"$line\"" >> /ragflow/conf/service_conf.yaml
+done < /ragflow/conf/service_conf.yaml.template
+
 # unset http proxy which maybe set by docker daemon
 export http_proxy=""; export https_proxy=""; export no_proxy=""; export HTTP_PROXY=""; export HTTPS_PROXY=""; export NO_PROXY=""