Sanitize error messages before capturing them

[simitt]

The go-docappender logs ES error.reason for troubleshooting purposes. Before logging, the part potentially containing preview data - Preview of field's value: '%s'- should be removed; see ES code

Example: https://github.com/elastic/go-docappender/blob/main/appender.go#L312-L319

[jkakavas]

@simitt is this resolved in 7.x too or isn't this a consideration/problem for that version ?

[simitt]

@marclop can you check if that behavior is the same in 7.17 please?

[marclop]

@simitt 7.17 uses the beats output, so as long as the beats team has fixed this issue for the libbeat 7.17 branch, it's not an issue for us.