The property for determining the contact uniqueness.

The link to a file in an external repository.
File Requirements:
Not empty
Delimiters - ","
Maximum size 100 MB
Requirement for column naming:
First name. The following rules apply to character usage:

• Max length: 40 symbols.
  - Letters from any alphabet are allowed (Unicode characters).
  - Three words longer than 3 characters and three words with a maximum of 3 characters are allowed.
  - Up to 3 digits are allowed.
  - Special characters are not allowed, except for:
  -- Apostrophes ''ʼ`´ʹʻʽʾʿˈˊˮʹ΄՚᾽᾿'‛′‵Ꞌꞌ＇ (only inside words)
  -- Hyphen - (only inside words)
  -- One dot at the end of words having max 3 characters. Example: Jr.
  - Names consisting only of numbers and special characters are not allowed
  Last name. The following rules apply to character usage:
  
• Max length: 40 symbols.
  - Letters from any alphabet are allowed (Unicode characters).
  - Three words longer than 3 characters and three words with a maximum of 3 characters are allowed.
  - Up to 3 digits are allowed.
  - Special characters are not allowed, except for:
  -- Apostrophes ''ʼ`´ʹʻʽʾʿˈˊˮʹ΄՚᾽᾿'‛′‵Ꞌꞌ＇ (only inside words)
  -- Hyphen - (only inside words)
  -- One dot at the end of words having max 3 characters. Example: Jr.
  - Names consisting only of numbers and special characters are not allowed
  Address
  Country
  Region
  City
  Postcode
  Email
  SMS
  Language code
  Timezone
  Contact ID
  Additional info
  The columns containing additional contact fields in a file shall be named: KEY_PROFILE.KEY_CUSTOMFIELD
  The fields that are not found in the system remain empty (not updated).

Event type identification key. An event of corresponding type is generated for each contact.
If the system does not have an event type with such a key, a new event type is created.
All characters are allowed, except < ; ’ \ / | " ` ' ^ ? ! , >
Max length: 100 symbols