feat(file-logger): add path properties to file-logger plugin metadata

[TaeyeongKwak]

Description

This PR adds path support to the file-logger plugin metadata, allowing a default log file path to be configured globally via plugin_metadata and used when an individual plugin config does not specify path.

For example, a user can set a path through plugin metadata, as below:

curl http://127.0.0.1:9180/apisix/admin/plugin_metadata/file-logger \
-H "X-API-KEY: $admin_key" -X PUT -d '
{
    "path": "logs/metadata-file.log"
}'

As above, if the path properties exists in the plugin metadata, you can exclude the path properties of the file-logger plugin when setting the route.

curl http://127.0.0.1:9180/apisix/admin/routes/1 \
-H "X-API-KEY: $admin_key" -X PUT -d '                                                                                                                                                                                                          
{
    "uri": "/hello",
    "plugins": {
        "file-logger": {}                                                                                                                                                                                                                             
    },
    "upstream": {
        "nodes": { "127.0.0.1:8000": 1 }
    }                                                                                                                                                                                                                                               
}'

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[ronething]

We have removed required = {"path"}, but it returns is required when path is empty. can we add something like neither the metadata nor the conf is configured

[Baoyuantop]

Hi @TaeyeongKwak, I submitted a suggested change and committed suggestion for this comment, but it seems the error message in the test also needs to be fixed. Could you please help me with that? It's located in t/plugin/file-logger.t. (TEST 1)

[TaeyeongKwak]

@Baoyuantop, I’ve fixed the error message in the test you mentioned.

[ronething]

others lgtm.