Extend AS tailer / header ( AS 4 )

This issue is to add the possibility of extending the AS_tailer and AS_header in Autosubmit,

The implementation should be something along the lines of:

Tailer:

Go to job/job_common.py

Find as_header/as_tailer functions,

Add a placeholder to the scripts.

###################
# Autosubmit tailer
###################
set -xuve
echo $(date +%s) >> ${job_name_ptrn}_STAT
touch ${job_name_ptrn}_COMPLETED
%EXTEND_TAILER% # <---
exit 0

Go to update_parameters functions in job.py

• Add a new parameter to export to job_level:

job.extend_tailer = #get_from_config
job.extend_header = #get_from_config

### PARAMETERS are what is used to export variables
PARAMETERS["EXTEND_TAILER"] = open(job.extend_tailer).read()
PARAMETERS["EXTEND_HEADER"] = open(job.extend_header).read()

• Add a new parameter to export to platform_level?

• Add a new parameter to export to wrapper_level

Autosubmit 3:

Add get_extend_tailer and get_extend_header to the config methods,