Add new check for OPeNDAP for granules

[binni979]

Overview
This pull request introduces a new check to verify the presence of OPeNDAP links in granule URL fields. The goal is to ensure that OPeNDAP links are included in the URL fields of granule metadata.
New Check Details
Check: Verify if OPeNDAP links are present in specified URL fields.
Fields:
Granule/OnlineResources/OnlineResource/URL (echo-g)
RelatedURLs/URL (umm-g)

Check Logic
The check inspects the specified URL fields for the presence of "opendap" in the URL.
If "opendap" is not found, a warning is generated, recommending the addition of an OPeNDAP link for this granule.

Implementation Steps
Added a new function, opendap_link_check, to perform the URL validation.
Added rule_mapping.json to include this new check.
Added checks.json to enable the OPeNDAP link check.
Added check_message.json to define warning messages for missing OPeNDAP links.

Testing
Tested Granules:
Granules that have opendap in URL, No opendap error was reported.

1. echo-g: G1463204472-LAADS
2. echo-g: G1479429385-LAADS
3. echo-g: G1689034590-OB_DAAC
4. umm-g: G2271018132-POCLOUD
5. umm-g: G2081781961-POCLOUD

umm-g: G1997478801-LARC_ASDC (Does not contain "opendap" in URL or have URL type "OPENDAP DATA") – Error: Warning generated to recommend adding an OPeNDAP link.