将附件转换到当前handler并且更新post中的链接, Covert attachments to current Handler

Created by: XuCpeng

@PutMapping("covert_attachment_handler")
    @ApiOperation("Covert all attachments to current Handler.")
    public Future<String> covertAttachmentHandler(
            @RequestParam(name = "sourceAttachmentTypeId", required = false, defaultValue = "-1") Integer sourceAttachmentTypeId,
            @RequestParam(name = "deleteOldAttachment", required = false, defaultValue = "false") Boolean deleteOldAttachment,
            @RequestParam(name = "uploadAllInAttachment", required = false, defaultValue = "false") Boolean uploadAllInAttachment,
            @RequestParam(name = "uploadAllInPost", required = false, defaultValue = "false") Boolean uploadAllInPost) {
        return attachmentHandlerCovertService.covertHandlerByPosts(
                sourceAttachmentTypeId,
                deleteOldAttachment,
                uploadAllInAttachment,
                uploadAllInPost);
    }

添加了一个接口，能够将附件库中的附件或者文章中的图片上传到“当前的图床”，并且更新post中的链接。基本原理是：正则提取post中markdown的的所有图片链接，用新的链接进行替换和更新。并且根据参数的设置，与附件中的链接进行比对，实现旧附件的删除或新附件的下载。

主要功能及参数如下：

• @param sourceAttachmentTypeId: 源图床ID (e.g. 0,1,2), 默认值为 -1 (所有图床).
• @param deleteOldAttachment: 是否从旧图床删除已经上传成功的附件，默认 false.
• @param uploadAllInAttachment: 是否上传源图床中所有附件，默认 false.
• @param uploadAllInPost : 是否抓取并上传post中的所有图片，默认 false.
• @return AsyncResult<String>

1. sourceAttachmentTypeId 可以通过方法 AttachmentType.getValue() 获得, 特别的是，-1 表示使用所有图床作为源图床。
2. 若 deleteOldAttachment = true, 旧的附件在上传成功后将从源图床删除。
3. 若 uploadAllInAttachment = true, 将会上传源图床所有附件，即使没有被post使用；若为false则只上传被post使用的附件。
4. 若 uploadAllInPost = true, 将会自动抓取下载post中的所有图片，并且上传到当前hanlder，无论是否在附件库中。

TODO：自动更新图库中的链接。当前还不能自动更新图库中的链接，所以对图库有强烈需求的不要删除旧附件。

未写前端，测试方法：

1. 在网页端登录后台，获取headers中的tocken

2. 在postman中创建一个PUT请求，请求地址为<blog host>/api/admin/attachments/covert_attachment_handler，并在Headers中加入该tocken，admin-authorization: <tocken>，参数按照上述添加即可。

3. 发送请求后将通过Async的方式执行，所以客户端会立即返回200，但实际的执行结果需要在spring.log中查看。方法完成后还会返回AsyncResult<String>，前端可以通过轮询获取结果。

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Added an interface to upload the attachments in the attachment library or the pictures in the article to the "current handler" and update the md link in the post.

• @param sourceAttachmentTypeId: source attachment type id (e.g. 0,1,2), default = -1 (All AttachmentTypes).
• @param deleteOldAttachment: Whether to delete old attachments, default = false.
• @param uploadAllInAttachment: Whether to upload all attachments, default = false.
• @param uploadAllInPost : Whether to download and upload all pictures in the all posts, default = false.
• @return AsyncResult<String>

1. sourceAttachmentTypeId can be gotten by AttachmentType.getValue(), In particular, -1 means to use all AttachmentTypes.
2. if deleteOldAttachment = true, Old attachments that have been successfully uploaded will be deleted from the specified Handler.
3. if uploadAllInAttachment = true, Will upload all attachments, even if they are not quoted by the post, default = false.
4. if uploadAllInPost = true, Will download and upload all pictures in the all posts, even if they are not in the attachment library.

No web, test method：

1. Log in to the admin on the web page and get the token in the headers.

2. Create a PUT request in postman, the request address is <blog host>/api/admin/attachments/covert_attachment_handler，and add the token in Headers, admin-authorization: <tocken>，the parameters can be added as described above.

3. After sending the request, it will be executed by Async, so the client will immediately return 200，But the actual execution result needs to be checked in spring.log. After the method is completed, it will return AsyncResult<String>, and the web can get the result through polling.

TODO：Automatically update the links in the gallery. Currently, the links in the gallery cannot be automatically updated, so do not delete old attachments if you have a strong demand for the gallery.