Implement meeting field

[alejandromumo]

Implement the field meeting considering its nested attributes:

• meeting.acronym
• meeting.dates
• meeting.place
• meeting.session_part
• meeting.session
• meeting.title
• meeting.url

Take into account the following requirements when implementing this field:

• It is needed in zenodo-rdm.
• It must be a custom field.
• It must be searchable. Search must be compatible with the current Zenodo search guide
• If needed, update DataCite serializer taking into account Datacite Schema 4.4 docs.
  • A recommended field RelatedItem can be used to serialize journal's information.
• The upload form should be similar to zenodo (e.g. meeting section is called Conference )