Split Gitlab Server comments if over max length

[krrrr38]

close #798

Motivation

If a comment is too long, a gitlab server returns a following error.

2019/10/03 03:07:12+0000 [EROR] command_runner.go:390 REPO_PATH_OBSCURED#247: Unable to comment: POST URL_OBSCURED: 400 {message: 400 (Bad request) "Note {:note=>["is too long (maximum is 1000000 characters)"]}" not given}

How to solve

Migrate implementation from other vcs server to split comment.

atlantis/server/events/vcs/azuredevops_client.go

Lines 99 to 109 in da981cb

	sepEnd := "\n```\n</details>" +
	"\n<br>\n\n**Warning**: Output length greater than max comment size. Continued in next comment."
	sepStart := "Continued from previous comment.\n<details><summary>Show Output</summary>\n\n" +
	"```diff\n"
	// maxCommentLength is the maximum number of chars allowed in a single comment
	// This length was copied from the Github client - haven't found documentation
	// or tested limit in Azure DevOps.
	const maxCommentLength = 150000
	comments := common.SplitComment(comment, maxCommentLength, sepEnd, sepStart)

[krrrr38]

https://docs.gitlab.com/ce/api/notes.html#create-new-merge-request-note

body (required) - The content of a note. Limited to 1,000,000 characters.