feat(license_import): Add endpoint to import licenses via a json file

[deo002]

Code Overview:

• Made a generic function InsertOrUpdateLicenseOnImport for creating/updating a single license on import. This function will be used in both Populatedb function and /licenses/import endpoint.
  -InsertOrUpdateLicenseOnImport takes input a map of license fields. This was done to accomodate updates of fields with zero values as valid values( ex. Risk can be 0, Active can be false ). GORM doesn't update fields with zero values when updating using a struct.
• Logic of addChangelogsForLicenseUpdate was kept seperate from InsertOrUpdateLicenseOnImport to make the latter generic. Populatedb won't need addChangelogsForLicenseUpdate.
• A new template datatype NullableAndOptionalData was introduced to differentiate between fields with zero values and fields with null values/undefined fields in json(in all the cases the unmarshalled struct will have zero values).
• InsertOrUpdateLicenseOnImport will be added to Populatedb in next PR to keep this PR size manageable.
• InsertOrUpdateLicenseOnImport returns errMessage and importStatus along with some license structs to make it generic. This was done because in endpoint, the relevant data will be added to response body while it will be logged in 'Populatedb'.

Behaviour:

• Inserts a new license to database if not already present(checks by shortname).
• Updates the license with new values if license already present.
• Updates the license with new values except for rf_text if rf_flag is set to 2(if this flag is set to 2, it means that the license text was updated manually and should not be updated via an import).

[GMishx]

Minor change needed.

[GMishx]

Changes looks good.

[GMishx]

Tested, working as expected.