provider/mesh: add doc comments
provider/mesh: add doc comments

prometheus/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,tyrken/alertmanager,brunoqc/alertmanager,Kellel/alertmanager,Aloomaio/alertmanager,brunoqc/alertmanager,joehandzik/alertmanager,joehandzik/alertmanager,GoogleCloudPlatform/alertmanager,Aloomaio/alertmanager,brancz/alertmanager,Aloomaio/alertmanager,brunoqc/alertmanager,tinytub/alertmanager,tyrken/alertmanager,tinytub/alertmanager,prometheus/alertmanager,tinytub/alertmanager,joehandzik/alertmanager,brancz/alertmanager,GoogleCloudPlatform/alertmanager,tyrken/alertmanager,Kellel/alertmanager,brunoqc/alertmanager,tyrken/alertmanager,brancz/alertmanager,prometheus/alertmanager,brancz/alertmanager,GoogleCloudPlatform/alertmanager,Kellel/alertmanager