Support multiple manifest into one single file

[olblak]

This pullrequest adds support for multiple Updatecli manifest into one YAML file.
Combined with the templating engine, this open the door to very advanced scenario but this also means complex manifest without jsonschema validation...

ps: worth mentioning by default if no pipelineid are defined, then they all share the same one

Fix #961

Test

To test this pull request, you can run the following commands:

cd pkg/core/config/
go test

Additional Information

Tradeoff

This feature allows to leverage the Golang templating with things like range such as in the following example

Simple manifest

values.yaml

names:
  - "Manifest 1"
  - "Manifest 2"

updatecli.yaml

{{- range $name := .names }}
---
name: {{ $name }}

sources:
  default:
    kind: shell
    spec:
      command: "echo 'Executing manifest {{ $name }}'"
{{- end }}

which shows

output

++++++++++++++++++
+ AUTO DISCOVERY +
++++++++++++++++++



++++++++++++
+ PIPELINE +
++++++++++++



##############
# MANIFEST 1 #
##############


SOURCES
=======

default
-------
The shell 🐚 command "/bin/sh /tmp/updatecli/bin/99aa0860859530c73d7b46e96b6a743321479b6f704e5ab92d961359e87fb0dd.sh" ran successfully with the following output:
----
Executing manifest Manifest 1
----
✔ shell command executed successfully


##############
# MANIFEST 2 #
##############


SOURCES
=======

default
-------
The shell 🐚 command "/bin/sh /tmp/updatecli/bin/2e064305c4cb4d9e1c4752a51558e7ff6338057f693aaf58b8bbc760e7050cfd.sh" ran successfully with the following output:
----
Executing manifest Manifest 2
----
✔ shell command executed successfully

=============================

REPORTS:



- Manifest 1:
	Source:
		✔ [default] 

- Manifest 2:
	Source:
		✔ [default] 

Run Summary
===========
Pipeline(s) run:
  * Changed:	0
  * Failed:	0
  * Skipped:	2
  * Succeeded:	0
  * Total:	2

Potential improvement

While looking into this I spotted the following improvement which would be useful:

• Allowing to load manifest from http/https endpoint, we already have the code in Updatecli...
  • After having a quick look this would slightly complicate the code while bringing little benefits so I am going to skip on this one
• Allowing to use json syntax, considering json is a subset of YAML. I did some early tests and everything seems to work as expected

• Allow Updatecli manifest/values to use JSON file #1463

• Adding to the go template the function toYaml from the sprig library feat: add yaml to/from functions Masterminds/sprig#360. I am considering adding the same function than the one used in helm as it will be exactly the same one that should be in the sprig library. This function would be the missing component to fix Feature Request: multiple/reusable configuration files #961

• Add various go template function from helm #1458

• the command updatecli manifest upgrade don't work with multiple manifest into the same file. I am not considering add the support in this pullrequest because I think this command should be rework anyway.